One might think that if one leg of an international trip was routed through a domestic airport, requiring a separate visa for the transfer of planes in that country, that the booking agency would alert travelers. One might think that, but hey! The world is full of surprises.

In the case of one Consumerist reader, who used a site called OneTravel to book a group’s flight roundtrip flights from Russia to the U.S. and back again, nary a red flag came up to call attention to a flight through a non-international German airport.

Kathy writes of her husband’s experience booking flights for a group of four friends coming to the U.S. from Russia. No problems on the trip out, but getting home ended up costing an extra $960 in change fees.

OneTravel never mentioned this when the original booking was made, nor in advertising for the flight. I think should be a violation of some type of disclosure law. And, if it’s not, they should make it a law.

How is any normal person supposed to know that if you go through certain airports during a routine layover, you might have to get a visa for a country you’re going to be in for four hours? The airline did notify them–weeks after the nonrefundable flight was booked — that they’d need to get German visas to sit in the airport. Not sure how much that would have cost, but they opted to change to a new flight, rather than make appointments and schlepp everybody to the Germany Embassy for visas, but were hit with the $960 in change fees. So their low-cost fare turned out to be pretty costly.

Sure, some savvy world travelers familiar with the name of every airport might be wise to such a loophole, but a more timely notification and flexibility in re-booking would be nice.

Make sure you check out each airport you’re flying through when traveling internationally, to avoid such a snag in your plans. As this story shows, using an agency doesn’t mean you’ll be in the know automatically, so do some research.

Want more consumer news? Visit our parent organization, Consumer Reports, for the latest on scams, recalls, and other consumer issues.