This is a Significant Operational milestone.
The first time a VTOL aircraft (not a helicopter) conducted a complete transition from vertical take-off to horizontal flight with a vertical landing. Conducted by a Convair XFY-1 Pogo. The pilot was James "Skeets" Coleman.
The aircraft first flew (untethered) on 01 Aug 1954
See AHS Calendar August 2014 for more details