Should I be paid for air travel time for a business trip?

You should be paid for your time anytime you are on company time, including your time traveling to and from the conference. They should also be paying for any meals, tolls, mileage you incur driving to and from the airport, parking costs, etc. Anything you have to pay for that you would not be paying for if you were not traveling for business purposes. Every company I have ever worked for has paid their hourly employees for this time. Salaried employees obviously only get paid expenses incurred.