Airborne forces were not unique to the D-Day landing plan

Was D-Day the only amphibious invasion to feature airborne troops?

No. Earlier operations in Norway and Crete also combined airborne assault with forces moving or arriving by sea.

Airborne troops had already been combined with maritime movement before 1944. Germany used airborne forces in Norway, while the assault on Crete began from the air and then depended on Italian amphibious troops as the defenders reorganized. D-Day refined a combined method rather than inventing it.