Having just returned from a short trip to Spain, travelling on a commercial airline is becoming harder and harder for photographers on a budget. So this post is not only my view but also something that may change what gear I currently use or choose in the future.
My current travel camera is my trusty Olympus E-M1, I carry this with a flashgun, two primes the 60mm macro and either the 17mm or the 25mm and two zooms, the 12-40mm and the 75-300mm. I fit all this and my 13″ Mac Book Pro and Kindle (essential for air travel, as I get bored flying) into an old Lowepro Mini Trekker AW. My tripod, filters, charger and power supplies go into checked in luggage. The carry on luggage usually weighs in about 10lbs, so currently is ok for all the UK budget airlines.

My well worn Lowepro Mini Trekker AW