Do it on business travel. Tons of scope for dissertation pontification there. Attitude of particular companies, if Fortune 500, compare it to CEO's pay, execs mode of travel, morale in the company as a result of policy, any patterns with certain companies, compare airlines and the entire experience from the minute you leave your front door to the minute you are home, regularity, see if you can relate the success of a company to how well it treats it employees when they travel, or how successful they are. Good luck.