Furthermore, the requirements specified for these aircraft narrowed down the field to only several models in production at that time, with most flight schools preferring the tandem-seat configuration of the Piper Cub. Seizing the opportunity unexpectedly thrust upon them, several light aircraft manufacturers quickly filled the market void with CPTP-compatible aircraft of their own, such as the WACO UPF-7 and the Meyers OTW biplane. Aeronca and Taylorcraft also produced tandem versions of their existing side-by-side seating high-winged monoplanes, each of which would lead to their own military equivalents.