Don't let them get you down shogun1A. Great minds seek the truth. Actually, it's a reasonable question.
There were a number of "airplanes" (here we mean powered aircraft, not gliders) that actually flew before 1903 so one has to pick a bit to be completely accurate. But why don't you check, for instance, the Wiki answer (yes folks, I know Wikipedia is not always the best but it looks reasonable enough in this case). See
Fixed-wing aircraft - Wikipedia, the free encyclopedia
You might also ask the teacher if he/she meant "practical" airplane.