If you were an hourly (not salaried) employee at the time of the earlier trip, and the training was *mandatory*--required by the employer, not merely supported, encouraged, etc.--then you should have been paid for the travel time. However, a wage and hour complaint may only be brought for 2 years after the time the claim arose--i.e. after the return date of the trip--so you may be out of, or just about out of, time. And, of course, taking legal action against your employer will have a drastic impact on your relationship with the employer; even without engaging in any provable illegal retaliation, they could, for example, not give you new opportunities coming up, or smaller raises or bonuses, etc. Think carefully about taking legal action for what may not be a large amount of money.