By glancing back, he is implying that the person behind him is something like a plain-clothes security officer (who should not be bribed)
I got that part, but why would you have to give bribes to African airport officials?
Right- I am confused by "avoided giving bribes" since typically bribes are something you go out of your way to provide.
I am guessing corrupt officials basically request money from you for no reason- and it's expected you give it to them (for no reason as well). Then, they just call it a "bribe". But I'm guessing... pardon my cultural ignorance.
There's quite a few airports around the world where you'll run into this sort of scam. In Guadalajara, I've had to pay a "fee" to board a flight that I already had a seat on. In Bangalore I had to pay another fee so that my luggage would not go missing or be damaged.
Could be to provide "motivation" to not search your bag for "contraband". A bribe to prevent artificially-created slow-downs.
He implied that the person behind him was some kind of anti-corruption agent