When I mouse over several flights at KSEA, I receive a pop-up window that says “Bellingham, WA” (Which is about 120 miles north of Seattle). This
seems to only be in the “Default” window. Moving in or out seems to stop it.
This is a really strange Firefox bug. When you hover over an airplane, you get a yellow tooltip that’s the same as the last tooltip you got from hovering over something else on the page. It’s one of our top priorities to get this fixed.
It is fixed in Firefox 12, which should be automatically pushed out to you soon. You can speed up the process by selecting Help, About Firefox. Let me know if this solves your problem.