While we're talking about making backup plans, Wikipedia is an AWESOME source for knowing direct destinations from any airport. The only issue is that "direct" does not necessarily mean "nonstop" but in many cases it does (and is easy to find out). For example, Guam shows up as a United destination from ORD, even though that flight is actually GUM-HNL-ORD. On the other hand, sometimes if I want to find a halfway city when going hub to hub (for example, ORD-CID-DEN) I can compare some of those lesser-known cities and get some ideas for what's doable.