Airport Status (free)

This app won't show delays for specific flights, but it will show general delays affecting U.S. airports. This is especially useful when your home airport is San Francisco International--due to low clouds, it often suffers from "ground stops" where flights are held at their departure airport until the weather improves. In the user comments for the app, some users were frustrated that Airport Status doesn't give them specific information for their flight. But that's not the point of this app. Rather, it shows the type of delay affecting an airport and how long it will last.

CXI Gaming makes a similar app with the same name (also 99 cents). It brings a bit more information and includes a U.S. weather map. FAA Wait (99 cents) also offers a few more features, but I prefer the simplicity of the free title. Air Travel and TSAWait (both 99 cents) originally displayed wait times at security checkpoints, but the Transportation Security Administration is no longer updating its Web site with that information. As such, they can offer only general delay data.