Airport Guide by iFly ($3.99)

Though frequent fliers may know their home airports like the back of their hands, they may occasionally land at an unfamiliar terminal. iFly can help in those situations. Its Airport Guide has detailed maps for airports around the world. You can view terminal diagrams for the locations of businesses and airline gates, research parking and ground transportation options, get recreation ideas for long layovers, and find related traveler services. It even offers a general history of the airport (perfect for real aviation geeks) and updates delay statuses.

iFly's Airport & Flight Guide ($6.99) offers all of the above plus real-time departure/arrival and flight tracking. And in a release due at the end of this month, iFly will add a feature that will let users navigate through terminals using diagrams that are overlaid on Google maps.

For other options, My Gate Maps ($2.99) uses the actual maps from airport Web sites. It's well designed and I like how if you're connecting through an airport you can plot your arrival and departure gates on the map. Airport Maps ($2.99) uses generic graphics, but it conveniently shows the location of not only shopping and dining options, but also airline lounges (iFly doesn't show the lounge locations). Common businesses like Starbucks and McDonald's are indicated by their logo. Airport Gates (99 cents) is another option, but I wasn't impressed.