In A Scandal in Belgravia Irene Adler shows the following text to Sherlock
007 Confirmed allocation 4C12C45F13E13G60A60B61F34G34J60D12H33K34K
and he figures out "these are seat allocations on a passenger jet" in several seconds.
I don't get it. If every "number-then-letter" combination in the string is a specific seat then there're only 14 people on the plane (a 747 which takes around four hundred people). Plus what's the point in planning which seats are taken without deciding who takes each seat? I don't see how this sequence could help anyone except Sherlock.
What exactly is in the string and how does it help plan the operation with the jet?