Well if you cannot increase the bandwidth (in frequency)
You can only switch to multiple spacial channels, and/or increase the power.
I guess they will go for a combination of both. Going to multiple spacial channels however is the harder part.
You can use multiple antennas, e.g. on different parts of the plane, and try to separate their signal with high directivity antennas. Or you can use reflections so your plane will not only use the direct link, but also nearby mountains to reach the other station.