Higher frequency means smaller and therefore lighter transformers, which is very important on aircraft. Nowadays a DC voltage supply would be better, but DC to DC voltage converters didn't exist when the 24V 400Hz standard was created.
For mains voltage we use 50-60 Hz because lower frequencies work better with very large AC generators in power plants and, and lower frequencies are more efficient to transmit long distances.
For mains voltage we use 50-60 Hz because lower frequencies work better with very large AC generators in power plants and, and lower frequencies are more efficient to transmit long distances.