Birds in Air - a nine patch block

one of the many blocks with this name , this is one of the simpler ones, basically you have one side of the half square triangle made from 9 smaller triangles.  Variations for the number of small triangles that make up the bigger half square triangle are the commonest variation with have four of the single blocks arranged together in a four patch as another.

Quilt codex include cutting instructions for a 9 inch block

Written instructions from Chock-A-Block for a block that is 8 inches finished.

this one is from adventures of a DIY mom and is a 9 inch block

and another from Eleanor Burns and Quilt In  A Day which makes the blocks using a two at a time method

This block is based on a 3x3 grid, for more 3x3 blocks click here