Status Prefix

(generally applied only to specific aircraft)

Mission Modifier prefix

Used when an aircraft has been modified for a different role from originally designed.

Mission Letter

Model Number

In theory each new design in a specific Mission category is numbered in sequence starting at 1, so that succeeding designs are numbered 2,3,4 etc. however numbers were occasionally skipped.

Sub-type

Minor modifications to a basic design are usually given a sequentially assigned letter denoting the particular subtype, starting with A and continuing with B, C, D, etc. In general, no additional meaning can be deduced from the sub-type letter.

Block Number

Analogous to the order number, these help not just to identify when an airframe was built, but in some types distinguish changes that occurred during production not identified by the sub-type letter, as between the Republic P-47 Thunderbolt razorback variant and the bubble canopy variant. Block numbers are unique to each type of aircraft.

Production facility code

Each factory producing aircraft for the USAAF was assigned a two letter code to distinguish between the product of one facility from another. This was important because parts were not always interchangeable between different plants, and the aircraft may have required different modifications during service.^[1]

Exceptions

Aircraft ordered by foreign governments but taken over by the US Government often used the manufacturer's internal designations rather than the designation used for similar aircraft ordered by the US Government, so that the Consolidated LB-30 was a B-24 ordered by the British but not delivered, and the Vultee V.77 was similarly an AT-19.