Washington National Airport is bikeable, mostly. Hopefully they have improved the last connections by now. It's right off the Mount Vernon Trail. I guess it's not technically an international airport, but I thought I'd mention it anyways.

I can cycle to my airport on quiet roads, but I haven't tried the actual approach to the airport. That might be trickier. I'll give it a go in the next few weeks. It's international because it has one flight to Toronto.