The plane would be in the beam path for only a short time: 900 Km/hour is 250 meters / second, if the beam were to be sent down very tightly the effect would be stronger but the duration would be correspondingly shorter.

A 100 meter diameter beam would take 0.4 seconds to cross, the energy density would be 12.75 W / square centimeter.

The kind of effect would also be quite dependant on the wavelength used, longer wavelengths would be harder to 'tight beam' than shorter ones.

A typical microwave oven 'beams' 1KW or so across an area about 15 cm radius, that's roughly 1.3 W / square centimeter.

How tight the beam is really is the crucial question to answer here, 35000 km up the beam will be very tight right under the point of emission, near the surface of the planet (an airliner flying 10 Km up) it would be much more dispersed.