The only way to get to Leticia is by boat or by air.
All foreigners must pay COP$20,000 tourist tax upon arrival at Leticia's airport, Aeropuerto Internacional Alfredo Vásquez Cobo, to the north of the town.
Trip and Tam fly from Tabatinga International Airport to Manaus daily. The airport is 4km south of Tabatinga; colectivos marked 'Comara' from Leticia will drop you nearby. Don't forget to get your Colombian exit stamp at Leticia's airport and, if needed, a Brazilian visa before departure.
When departing Letica's airport, all foreigners must check in at the Ministry of Foreign Relations before proceeding through airport security, regardless of whether you've left Colombia or not; you'll be directed there at check in if you haven't done it already – it's a painless procedure that takes a matter of seconds.