Gadling's guide to getting bumped: Checking flight loads

When you step onto your favorite airplane, normally you only see two classes of service -- First and Coach. Occasionally you'll also see a Business and Coach Plus section (especially on international flights), but for 90% of flights you'll only see the big comfy seats in front and the cramped seats in back.

In reality, there are over a dozen classes available in a flight, labeled anywhere between A and Z. These classes correspond to a certain set of fare rules, price and benefit respectively. As an example, here is how frequent flyer miles are accumulated on your typical Northwest flight:

Elite Qualifying Miles at 150%: P, F, J, C, I, Z, Y, B
Elite Qualifying Miles at 100%: M, H, Q, V, L, T, K
Elite Qualifying Segments: P, F, J, C, Z, Y, B, M, H, Q, V, L, T K

I'll get to Elite Miles some other time.

What you need to check for before departure is whether or not your flight is full -- after all, it doesn't make any sense to do your homework if there is no test. My favorite tools for checking availability are seatcounter and the Amex availability tool. For experienced travelers you can also use the KVS availability tool or Expertflyer. You have to pay for the latter two utilities, but they give you a little more flexibility and power. I've tried both Expertflyer and the free tools, and seatcounter works just fine for me.

It could take weeks to research and explain the exact meaning and effect of each fare class on each airline, so I'll tell you what you basically need to look for. Plug in your flight data into the system and read across how many tickets are available in the fare classes. If you see zeros across the board, your flight is probably completely full. Even if you see a couple of ones and mostly zeros, the flight could max out and overbook by the time you get to the airport so it could be worth vying for the bump.

For my flight to Los Angeles next Sunday, I've got:

B9 F5 H6 K0 L0 M9 P9 Q4 T0 V4 Y9

That's a lot of numbers and letters, but not a lot of zeros. Flight's not full now, but I'll check back on Saturday.

But for my flight to New York on Friday, I've got:

B0 H0 K0 M0 Q0 V0 Y0.

That's a full flight.

Alternatively, you can call the airline or ask the ticket agent at the day of the departure. They're obligated to divulge this information to you, so if you ask "is the flight overbooked?" they have to tell you.

Next you want to prepare yourself to get into an argument with the gate agent.