OpenFlights is promising, and the developer is very enthusiastic: FlightMemory import was broken and he fixed it within a couple of hours after I emailed him.

The only thing that I take issue with is that there's no info on privacy/data protection/t&c. If I use a service that stores pretty personal information I - for example - wouldn't mind knowing they're going to keep it confidential.

I'm sure he has no malicious intentions, but either way, I'm just a little bit uneasy.