A-2278 in its final form. Note the marked dihedral of the upper wing and anhedral of the lower wing.

Curtiss HA A-4110. Note the radiator details and three-bladed airscrew.

The second HA, A-4110, taxying, December 1918. Note the high position of the pilot. It is not known if he sat lower when in flight.

A-4110 on December 23, 1918. Note the short span ailerons and two-bladed propeller.

The third and last HA was A-4111. It bears the star in circle insignia. Note the conventional cabane strucure made necessary by the increase in wing area.

HA mailplane with short span wings at Roosevelt Field, January 15, 1919.

Curtiss photograph B176 dated May 15, 1918. Nose radiator developed for the HA after the early radiator proved to have too small a cooling area. This radiator with the vertical header tank and overflow pipe was fitted to A-2278.

HA mailplane with two bay wings and a conventional cabane has been fitted.

Curtiss publicity line-up of HA Mailplane, Oriole and Type 18B.

HA Mailplane under construction.

Curtiss HA A-2278 in its final form with enlarged tail surfaces, unbalanced rudder and nose radiator.

HA A-4110 was finished in the US Navy scheme of grey overall with AEF-style roundels to the wings. This view gives a good idea of the corpulent size of the fuselage.

Curtiss HA A-2278 in its original form. Note the small fin and balanced rudder.