Weis-Fogh was research assistant to the Danish Nobel Prize–winning physiologist August Krogh, where he studied the flight mechanism of the desert locust.

[12] Weis-Fogh then went to the University of Cambridge in England for four years, where he discovered a rubbery protein, resilin, in insect cuticle.

[12][24][25][26][27][28] In 1973 Weis-Fogh devised a mathematical model explaining how extremely small insects such as thrips and chalcid wasps such as Encarsia formosa could fly using clap-and-fling,[29][30] where conventional steady state aerodynamics did not apply.

These insects gain lift by creating vortices near their wings, at the price of the wear and tear from repeated clapping.

[12][13] Weis-Fogh's 1973 paper Quick Estimates of Flight Fitness in Hovering Animals, Including Novel Mechanisms for Lift Production[29] has been cited over 1000 times.