By Priya Anand, Backpacking Gear Research Writer · Published September 14, 2026, 6:03 PM ET · Updated September 29, 2026, 6:16 PM ET
Direct Answer
Often, yes, if the packed bag stays within the airline's cabin bag limits; liter count alone doesn't decide it. Delta, for example, allows 22 x 14 x 9 inches (45 linear inches), and other airlines set their own limits. Compression straps help cinch a packed bag down to fit gate sizers.
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In plain English
Airlines don't care how many liters a backpack holds. They care whether it fits in the metal frame at the gate, called a sizer, that matches their size limit. The liter number tells you how much a pack can hold, like the capacity printed on a jug, but two 40-liter packs can have very different shapes. A stuffed side pocket or a bulging top lid can push a pack past the limit even when its liter number looks small.
What's inside the pack matters too. Airport security keeps its own list of items that can't go in the cabin, and several of them are ordinary hiking gear: stove fuel, bear spray, knives and poles with sharp tips. The simplest habit is to pack the bag exactly the way you'll fly, measure it with a tape, and read both the airline's baggage page and the security rules before you leave home.
Whether a hiking backpack qualifies as a carry-on depends on its packed dimensions matching the airline's stated cabin bag limits, not on its liter volume alone. A 40-liter pack with a slim, boxy shape can clear a gate sizer more reliably than a 35-liter pack with bulging side pockets.
What size limits apply
Delta, for example, caps carry-on bags at 22 x 14 x 9 inches, or 45 linear inches combined, and other airlines publish their own limits. Some international and budget carriers set smaller limits, and many budget airlines separate a small free "personal item" from a larger paid cabin-bag allowance.
Situation
What to check
Domestic US flight
The airline's published limit (Delta's is 22x14x9in), enforced by gate sizers on full flights
International or budget carrier
Often a smaller limit; some airlines charge extra for a full-size cabin bag
Multi-airline itinerary
Size the pack to the smallest limit among all airlines on the trip
How to improve the odds of clearing a gate check
Compression straps cinched down after packing pull in loose fabric and flatten a pack's overall footprint, which matters most on a half-packed bag. A pack with a boxy, minimally padded silhouette and a structured base panel holds its packed shape more consistently than one with rounded side pockets or a floating lid, both of which add inches in ways that don't show up in the stated liter count.
Travelers with a tight, multi-leg itinerary should treat the smallest airline's limit as the real requirement, since a bag that clears a US domestic flight can still be pulled aside on a connecting international or budget-carrier leg.
Linear inches, and why one airline's number isn't everyone's
Airlines usually publish a carry-on limit two ways: three maximum dimensions and a combined total. Delta, for example, lists 22 x 14 x 9 inches (56 x 35 x 23 cm) and a 45-linear-inch (114 cm) total.1 The combined figure is length plus width plus depth, but each single dimension still has to fit. Depth is where hiking packs usually fail: 9 inches disappears quickly once a padded back panel, a hipbelt and a full front pocket stack up.
Some guides describe 22 x 14 x 9 inches as common on US carriers. The only airline source in this site's research library is Delta, so treat that size as one airline's published rule rather than a national standard, and check every carrier on your ticket. Weight limits for carry-on bags also vary and aren't covered by a verified source here, so look them up per airline instead of assuming.
Delta also says a small backpack can count as the free personal item if it fits under the seat in front of you.1 For a hiker, that allows a useful split: the main pack as the carry-on, and a packable daypack as the personal item for snacks, a jacket and documents.
The gear rules catch hikers more often than the size rules
A pack that fits the sizer can still be stopped at the checkpoint. TSA prohibits flammable liquid fuels, including cooking fuel, in both carry-on and checked bags.2 A camp stove can travel in either bag only if it is completely emptied of fuel and cleaned so no vapor or residue remains, and the officer at the checkpoint makes the final decision.3 Bear spray is listed as not allowed in carry-on or checked bags.4
Poles depend on the tip. Blunt-tipped hiking poles are allowed in the cabin, but sharp-tipped poles are not.5 Tent poles are generally allowed in either bag.6 Knives can't go in carry-on bags unless they are rounded, blunt and non-serrated, such as butter knives; in checked bags, sharp objects should be sheathed or securely wrapped.7 One book of safety matches is allowed in the cabin, while all matches are banned from checked baggage.8
Hikers flying carry-on only usually plan to buy fuel and bear spray at the destination. Some places add their own twist: at Isle Royale, carrying fuel canisters on the seaplanes that serve the park is unlawful, so visitors buy fuel on arrival.9
Measuring a packed pack honestly
Measure after packing, never empty. Load the pack with exactly what you'll fly with, cinch the compression straps, then measure the longest, widest and deepest points, including the hipbelt. The Appalachian Mountain Club treats cinching the external compression straps as the final packing step because it shrinks and stabilizes the load.10 If the depth still runs over, move soft bulk into the personal-item bag or wear your heaviest layer onto the plane.
Frames matter at the margins. A pack with a stiff framesheet or aluminum stays can't be squashed into a sizer the way a frameless bag can, so a framed pack has to meet the limit on its own shape.
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