There are variables, but for a pack that can be carried aboard a jetliner, youre looking at around 3,000 cubic inches, maybe a bit more. You probably could get away with 3,500 cubic inches. And thats quite a bit, really. Especially if you re-think your load, which Ill get to momentarily.
For a pack, the REI Tour Travel Pack ($145; rei.com) is a pretty good unit made up of a primary pack and a detachable daypack. With the daypack attached, the unit might be too big to carry aboard. But if you detach the daypack, you can carry on the primary pack and claim the daypack as a personal item, so youre OK. And theres nothing wrong with The North Face Terra 40 ($109; thenorthface.com), but its really just a big day pack.
If this were my trip, I might get the REI pack, but probably would go for the Osprey Atmos 50 ($199; ospreypacks.com). Why? Because its a GREAT packpretty roomy (3,000 cubic inches), light (at just over 3 pounds), and very comfortable. It would carry on nicely and manage those days when the pack is on your back quite a bit. I also like Eagle Creeks Voyage ($185; eaglecreek.com), which has the removable daypack shtick but still is a nice travel pack and can be carried on.
OK, pack taken care of. Now for your gear. What the bloody hell are you carrying? A sleeping bag thats 7X14? A tent thats 7X23? Good lord, this is the 21st century, youre taking a SUMMER trip, and youre packing like Scott of the Antarctic. Get yourself a Marmot Arroyo ($249, one pound, eleven ounces; marmot.com) or a MontBell 30-degree Down Hugger ($270, one pound, seven ounces; montbell.com). Both pack down to the size of a cantaloupe. Then get a Mountain Hardwear Meridian 1 tent ($170, just under four pounds; mountainhardwear.com). Give it a good squish and its half the size of what you propose to take.
Youre buying a plane ticket, youre taking the summer off, you can afford both. Dont even bother to thank me.
The Gear Guy reports from 2007 Winter Outdoor Retailer, the bi-annual gearapalooza in Salt Lake City. Check out his top picks for gear to watch in 2007.