The first cover is a 3.15 pesos Via Condor cover to Germany.
The second cover is a 3.45 pesos cover to Austria, apparently with 10 centavos in excess postage if we are to believe the penciled 3.35 pesos is a mark made by the postal clerk.
A Stamp Collecting Blog Dedicated to one of the Most Interesting Series of the 20th Century
The first cover is a 3.15 pesos Via Condor cover to Germany.
All three are 2.15 pesos rates (none are registered). The first is Via Condor to Germany.
These are all 1.15 pesos rates. The first cover was mailed Via Condor.
All three are 1.10 pesos rates. As is typical for covers to the United States, the name of the airline is not on the front of the cover, and like many covers not registered, there are no transit or receipt marks on the back.
The first cover was postmarked October 24, 1935, and mailed to Germany.