Tony's Indian stamps are always interesting.
Liking the Penny Blacks as well (need to get one of those!)
Here are some classic airmails for 2013:
1923 De Haviland Biplane, Plate Number Single, US, Scott #C6

1926 Mail Plane, Egypt, Scott #C1

1929 Bird Carrying Letter, Switzerland, Scott #C15

1933 Allegorical Figure of Flight, Switzerland, Scott #C12a (grilled gum)
