The question is what you're trying to accomplish. If you're trying to prevent people from calling in planes, the cell phone network does a pretty good job of jamming itself.
The plane will be fine from the jammer. For 900 MHz, 935 V/m=2.3 kW/m^2=231 mW/cm^2. That's 231 times the safety limit of 1 mW/cm^2. The RF concern with cell phones in planes isn't the 900 MHz emissions, but the harmonics that leak out into the HF and VHF comm ranges. That's the same reason why you can't use a broadcast radio receiver in planes.