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Comparison

Aer Travel Pack 4 vs Peak Design (2026)

Aer’s Travel Pack 4 35L is a 35 L, 3.90 lb pack listed at $259, with official dimensions of 21.5 × 13.5 × 9 inches; the official page was sold out on November 10, 2026. Peak Design’s Travel Backpack 45L is $299.95 and 4.5 lb, with a written 35 L “max carry-on” standard size of 22 × 13 × 9.5 inches that expands to 45 L and 11 inches deep. Peak’s 30L, at $249.95 and 3.17 lb, is the closer official fit to United’s 9 × 14 × 22 in box. We compared those written specs, not a packing test.

By PickedTravel Editorial TeamLast updated Prices & specs checked Nov 10, 2026

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How this page was made: this is a research-based guide built from manufacturer spec pages, official prices and published lab measurements from the outlets we name and link. We haven’t tested these products ourselves, and we don’t invent scores. Our methodology.

Quick answer

Choose Aer’s Travel Pack 4 35L if you want official 21.5 × 13.5 × 9 in, 35 L and 3.90 lb, inside United’s 9 × 14 × 22 in box, plus a defects-only warranty. Choose Peak’s 45L for official 35–45 L expansion; its 9.5 in depth sits over United’s 9 in. Peak’s 30L is the closer official United fit.

Last updated Prices checked Nov 10, 2026

Check Aer Travel Pack 4 35L price (opens in a new tab)Check Peak Design Travel Backpack 45L price (opens in a new tab)

Key facts at a glance

Key facts (prices checked Nov 10, 2026)
Aer Travel Pack 4 35LPeak Design Travel Backpack 45L
Price (USD, Nov 10, 2026)$259; official page was Sold Out$299.95 (Black, SKU BTR-45-BK-2, available in the fetch)$249.95 (Black, SKU BTR-30-BK-2, available in the fetch)
Official exterior size21.5 × 13.5 × 9 in (54.5 × 34 × 23 cm). No expansion figure on the official page we fetched.Standard / compressed: 22 × 13 × 9.5 in (56 × 33 × 24 cm). Official note: compression “only happens at the top of the bag. 6 in at top when compressed.” Expanded: 22 × 13 × 11 in (56 × 33 × 29 cm).Standard: 20.9 × 13 × 7 in (53 × 33 × 18 cm). Expanded: 20.9 × 13 × 7.9 in (53 × 33 × 20 cm).
Capacity, as written35 L (a single official volume; no compressed/expanded split)Standard (max carry-on): 35 L. Compressed: 30 L. Expanded: 45 L.Standard: 27 L. Expanded: 33 L. Official marketing: meets international carry-on size requirements in expanded (33 L) and compressed (27 L) form.
Weight3.90 lb2.05 kg (4.5 lb)1.44 kg (3.17 lb)
Vs United 9 × 14 × 22 in incl. handle and wheels21.5, 13.5 and 9 in all sit inside the published box.Height 22 in matches; width 13 in sits inside; depth 9.5 in is over the published 9 in. Expanded 11 in is further over. Peak’s “international carry-on” claim is not the same as United’s published box.20.9 × 13 × 7 in, and 20.9 × 13 × 7.9 in expanded, all sit inside the published box.

We compared official pages for Aer’s Travel Pack 4 35L and warranty, Peak Design’s Travel Backpack product page (30L and 45L specs and prices on that official page), Peak Design’s lifetime warranty, and United’s carry-on limit, all fetched November 10, 2026. Aer’s official 35L page was sold out at $259 when we fetched it; we are not pretending it is in stock. We have not packed or sizer-tested these bags, and we do not invent scores. Peak Design’s “meets international carry-on size requirements” language is quoted as marketing, then checked against United’s published 9 × 14 × 22 in box, including handles and wheels.

For a duffel versus a wheeled spinner, see weekender vs carry-on. For hardside carry-ons, see best carry-on luggage.

Aer Travel Pack 4 35L
Peak Design Travel Backpack 45L

Aer Travel Pack 4 35L vs Peak Design Travel Backpack 45L: side-by-side

Aer Travel Pack 4 35L vs Peak Design Travel Backpack, official pages fetched November 10, 2026
Aer Travel Pack 4 35LPeak Design Travel Backpack 45LPeak Design Travel Backpack 30L (same official page)
Price (USD, Nov 10, 2026)$259; official page was Sold Out$299.95 (Black, SKU BTR-45-BK-2, available in the fetch)$249.95 (Black, SKU BTR-30-BK-2, available in the fetch)
Official exterior size21.5 × 13.5 × 9 in (54.5 × 34 × 23 cm). No expansion figure on the official page we fetched.Standard / compressed: 22 × 13 × 9.5 in (56 × 33 × 24 cm). Official note: compression “only happens at the top of the bag. 6 in at top when compressed.” Expanded: 22 × 13 × 11 in (56 × 33 × 29 cm).Standard: 20.9 × 13 × 7 in (53 × 33 × 18 cm). Expanded: 20.9 × 13 × 7.9 in (53 × 33 × 20 cm).
Capacity, as written35 L (a single official volume; no compressed/expanded split)Standard (max carry-on): 35 L. Compressed: 30 L. Expanded: 45 L.Standard: 27 L. Expanded: 33 L. Official marketing: meets international carry-on size requirements in expanded (33 L) and compressed (27 L) form.
Weight3.90 lb2.05 kg (4.5 lb)1.44 kg (3.17 lb)
Vs United 9 × 14 × 22 in incl. handle and wheels21.5, 13.5 and 9 in all sit inside the published box.Height 22 in matches; width 13 in sits inside; depth 9.5 in is over the published 9 in. Expanded 11 in is further over. Peak’s “international carry-on” claim is not the same as United’s published box.20.9 × 13 × 7 in, and 20.9 × 13 × 7.9 in expanded, all sit inside the published box.
Materials and access, as written1680D CORDURA ballistic nylon exterior and ripstop nylon interior (both bluesign approved); YKK zippers; lay-flat main compartment; padded 16" laptop pocket; luggage pass-through; hidden smart-tracker pocket; lockable zippers; optional hip belt sold separately.Weatherproof 100% recycled 400D nylon canvas shell with 900D bottom liner; top, side, front and rear access via #8 and #10 UltraZips; 16" laptop sleeve (official max 16 × 11 × 1 in); tuck-away straps and built-in hip belt; packing-cube capacity “3 units + bonus space.” Fair Trade Certified and 100% carbon neutral, as written.Same recycled 400D / 900D family. Official page: main access via a large rear hatch (simplified versus the 45L’s extra side and front access); optional hip belt accessory, not built in; packing-cube capacity 3 units; 16" laptop sleeve.
Warranty, as writtenLifetime warranty for manufacturing defects in materials or workmanship, original purchaser (or original gift recipient), not transferable. Not covered: normal wear, accidental damage, misuse, third-party repairs, cosmetic issues, unauthorized or second-hand purchases. U.S. inbound shipping covered only in the first year; after that, the customer pays shipping to Aer, and Aer covers the return shipment.Lifetime warranty covers manufacturing defects and failures or breakages that make the product non-functional. Not covered: cosmetic wear, misuse, neglect, accidents, or intentional damage; stolen or lost items; Factory 2nd products. Official page: replacements may be open-box, gently used, or refurbished, quality-checked and still under the lifetime guarantee.Same Peak Design lifetime warranty as the 45L.

What are the pros and cons?

Aer Travel Pack 4 35L: pros

  • Official 21.5 × 13.5 × 9 in and 35 L sit inside United’s published 9 × 14 × 22 in box, with no expansion zipper to take it over that box.
  • Lighter than the Peak 45L (3.90 lb vs 4.5 lb) at the same official 35 L standard volume.
  • Official $259 list is below the Peak 45L’s $299.95, if you can actually buy it.

Aer Travel Pack 4 35L: cons

  • The official page was sold out at $259 on November 10, 2026.
  • No official expansion, and the lifetime warranty excludes accidental and airline-style damage, with inbound U.S. shipping covered only in year one.
  • Single official volume and access layout — no Peak-style compressed/expanded split on the page we fetched.

Peak Design Travel Backpack 45L: pros

  • Official expansion from a 35 L “max carry-on” standard to 45 L, plus front, side and rear access and a built-in hip belt.
  • Lifetime warranty covers functional failures, not only manufacturing defects, and does not require a first-year shipping cutoff in the official wording we fetched.
  • A 30L sibling on the same official page lists a tighter 20.9 × 13 × 7–7.9 in size at $249.95 and 3.17 lb.

Peak Design Travel Backpack 45L: cons

  • Official standard depth of 9.5 in, and expanded 11 in, sit over United’s published 9 in, despite “international carry-on” marketing.
  • Heavier and more expensive than Aer’s 35L at the official 35 L standard volume ($299.95 and 4.5 lb).
  • Warranty replacements may be open-box or refurbished, and accidents are excluded.

Which should you choose: Aer Travel Pack 4 35L or Peak Design Travel Backpack 45L?

If United’s published 9 × 14 × 22 in box is your bar, Aer’s official 35L dimensions fit, and Peak’s official 30L dimensions fit; Peak’s official 45L standard depth of 9.5 in does not. If you want a written expansion from 35 L to 45 L and extra access zips, the 45L is the official Peak match — just treat “international carry-on” as a claim to check in a sizer, especially when expanded. Confirm live stock: Aer’s 35L page was sold out at $259 when we fetched it.

Choose Aer Travel Pack 4 35L if…

  • You want official 35 L dimensions that sit inside United’s published box, with no expansion zipper.
  • You prefer a 3.90 lb empty weight and a $259 list price, and you can wait for restock or buy from an authorized retailer with valid proof of purchase.
  • A manufacturing-defect warranty is enough, and you accept that accidental or airline damage is excluded.
Check Aer Travel Pack 4 35L price (opens in a new tab)

Choose Peak Design Travel Backpack 45L if…

  • You want official expansion to 45 L and 11 in deep, plus front and side access, and you will check a sizer before boarding.
  • You would rather buy the Peak 30L ($249.95, 3.17 lb, 20.9 × 13 × 7–7.9 in) for a closer official United fit.
  • You want Peak’s official lifetime functional-failure warranty, and you accept that replacements may be refurbished and that accidents are still excluded.
Check Peak Design Travel Backpack 45L price (opens in a new tab)

Capacity looks similar until you read the depth

Aer’s Travel Pack 4 35L is a single official volume: 35 L, 21.5 × 13.5 × 9 in, 3.90 lb, $259. Peak Design’s 45L lists a standard “max carry-on” volume of 35 L at 22 × 13 × 9.5 in, then expands to 45 L at 22 × 13 × 11 in, and can compress at the top to a 30 L official capacity (the official page says compression only happens at the top, with 6 in at the top when compressed). Those are not the same 35 L bag. The Peak 45L’s official standard depth is already 0.5 in over United’s published 9 in; expanded, it is 2 in over.

Peak’s official 30L is the size that actually sits inside that United box on paper: 20.9 × 13 × 7 in standard, 20.9 × 13 × 7.9 in expanded, 27 L / 33 L, 3.17 lb, $249.95. Peak’s marketing says the 30L “meets international carry-on size requirements in expanded (33 L) and compressed (27 L) form.” We still want a sizer check, but the published numbers are inside United’s box, unlike the 45L’s official 9.5 in depth.

Warranties and stock

Aer’s official lifetime warranty covers manufacturing defects in materials or workmanship for the original purchaser or original gift recipient, and it is not transferable. It does not cover normal wear, accidental damage, misuse, third-party repairs, cosmetic issues, or purchases from unauthorized or second-hand sources. For U.S. claims, Aer covers inbound shipping only in the first year; after that, you pay to ship the bag in, and Aer pays to ship it back.

Peak Design’s official lifetime warranty covers manufacturing defects and failures that make the product non-functional. It does not cover cosmetic wear, misuse, neglect, accidents, intentional damage, or lost or stolen items. Official wording says replacements may be open-box, gently used, or refurbished items that have been quality-checked and still carry the lifetime guarantee. Neither official warranty is a promise to fix airline mishandling.

Stock matters on this comparison. Aer’s official 35L page listed $259 and Sold Out on November 10, 2026. Peak’s official Black 30L and 45L variants were listed as available in that fetch. Confirm live inventory before you treat either bag as a buy.

Who should skip this comparison

  • Shoppers who want a wheeled carry-on or a weekender duffel. Use best carry-on luggage or weekender vs carry-on.
  • People who need an under-seat personal item. These packs are carry-on backpacks, not personal-item bags. See best personal item bag.
  • Anyone who needs a bag that is in stock today at Aer’s official price. The Travel Pack 4 35L page was sold out when we fetched it.
  • Travelers who treat “international carry-on” as a guarantee of United’s 9 × 14 × 22 in box. Peak’s official 45L standard depth is 9.5 in.

Frequently asked questions

Which bag actually fits United’s published carry-on box?
On official numbers, Aer’s 21.5 × 13.5 × 9 in 35L sits inside United’s 9 × 14 × 22 in box, including handles and wheels. Peak’s 30L official sizes (20.9 × 13 × 7 in, or 7.9 in expanded) also sit inside. Peak’s 45L official standard size is 22 × 13 × 9.5 in, which is over the published 9 in depth, and the expanded 11 in is further over. We have not put the bags in a sizer.
Is the Peak 30L or 45L the fair comparison with Aer’s 35L?
The official 45L standard volume is 35 L, the same number Aer prints, so that is the capacity match — with a larger official footprint and an expansion to 45 L. The official 30L is closer in empty weight and is the better published United fit. We table both instead of hiding the 30L.
Is the Aer Travel Pack 4 35L in stock?
Not on the official product page we fetched November 10, 2026, which listed $259 and Sold Out. Check the live page or an authorized retailer. Aer’s warranty requires an order number from aersf.com or valid proof of purchase from an authorized retailer.
Do these warranties cover airline damage?
Not on the official pages we fetched. Aer excludes accidental damage and misuse. Peak Design excludes accidents, neglect, and cosmetic wear. Neither page describes an airline-mishandling benefit like some suitcase programs.
Can I use a laptop in either pack?
Yes, on official wording. Aer lists a padded, suspended pocket that fits a laptop up to 16 inches. Peak Design lists a 16 inch laptop sleeve on both the 30L and 45L, with official max dimensions of 16 × 11 × 1 in.

Sources

Pricing and plan details were checked on the official pages below as of Nov 10, 2026. Vendors change prices, credits and plan names often, and some show regional pricing at checkout, so confirm on the vendor’s site before you buy.

  1. Aer: Travel Pack 4 35L official product page — $259 sold out, 21.5 × 13.5 × 9 in, 35 L, 3.90 lb (fetched Nov 10, 2026) (aersf.com)
  2. Aer: Warranty — lifetime manufacturing defects, exclusions, first-year U.S. inbound shipping (fetched Nov 10, 2026) (aersf.com)
  3. Peak Design: Travel Backpack official product page — 30L and 45L prices, dimensions, capacities and weights (fetched Nov 10, 2026) (peakdesign.com)
  4. Peak Design: Warranty — lifetime defects and functional failures; exclusions and refurbished replacements (fetched Nov 10, 2026) (peakdesign.com)
  5. United Airlines: Carry-on bags — 9 × 14 × 22 in including handle and wheels (fetched Nov 10, 2026) (united.com)
guide

Weekender vs Carry-On (2026)

Choose a weekender duffel if you want a lighter soft bag you can shoulder or stack on a roller — Away’s Weekender is $248, 38 L, and 3.8 lb with the strap, but Away’s own FAQ says it is not a personal item and is too large under a seat when fully packed. Choose a wheeled carry-on if you want a structured spinner with a built-in lock and a suitcase warranty; Away’s Carry-On is $275 and about twice the empty weight, with official size figures that conflict across Away’s own pages. Confirm the packed bag in a sizer. United’s published limit is 9 × 14 × 22 inches including handles and wheels.

best of

The Best Weekender Bag for a Short Trip

If you want more listed capacity for less money, BÉIS The Weekender is $118 and 42 L — but its official 15.75 in height and 9.84 in depth sit over United’s published 9 × 14 × 22 in carry-on box, while they sit inside Frontier’s 24 × 16 × 10 in carry-on box. Away The Weekender is $248 and 38 L, closer to United’s published box (9.4 in vs 9 in on one side), and Away’s own FAQ says it is a carry-on, not a personal item.

best of

The Best Carry-On Luggage for Holiday Travel

If you need a bag that matches United’s published 9 × 14 × 22 in limit (wheels and handle included), Monos’ official Carry-On dimensions do. Travelpro’s Maxlite 5 is much lighter and cheaper, and Away’s The Carry-On sits slightly over that published box on two dimensions — confirm with a sizer.

best of

The Best Personal Item Bag for Holiday Flights

If you need a bag that sits inside Frontier’s published 18 × 14 × 8 in personal-item box (handles, wheels and straps included), the official dimensions for Away’s Everywhere Bag and the Monos Metro Duffel do. BÉIS’s Mini Weekender lists more capacity, but its 15.75 in height is over Frontier’s published 14 in limit — and all three official sizes sit over United’s tighter 9 × 10 × 17 in box on at least one side.

guide

Hardside vs Softside Luggage (2026)

On official pages fetched November 10, 2026, Away describes hardside as an impact-resistant polycarbonate shell starting at $275, softside as abrasion- and water-resistant nylon starting at $225, and aluminum as a premium hard shell starting at $625. Monos, which sells polycarbonate and aluminum cases, not a softside line on the pages we fetched, says its German Makrolon polycarbonate flexes under impact and springs back. We compared those written material claims and the conflicting official measurements, not a drop-test scorecard. Confirm dimensions, including wheels, in an airline sizer.