Planes in the sky are easy, a simple 1/4 wave ground plane will work. The tower and planes on the ground are going to be a challenge. To cover the distance you would get the best results with a yagi pointed in each direction. You will still be able to hear planes in the air at over 50 miles in any direction with a yagi. You get a very large signal increase due to height gain and yagis still have some gain off of the sides and back. You can probably hear the tower but it's not likely you will hear planes on the ground. The path loss will be greatly increased by any ridges/hills in the path. Getting your antennas as high as possible will be the best way to improve coverage. If you could send me Lat/Lon coordinates for all four locations I could run some path analysis plots and send them to you.
If you use two yagis, a phasing harness (a 1/4 wave run of 75 ohm coax to each yagi) is not really going to add any signal as the front/back ratio of the yagis will leave very little signal from the opposite yagi. A phasing harness will combine the two signals and provide a 50 ohm match for each antenna. I highly recommend a mast mounted preamp with a FM band notch or a AirBand bandpass filter.
Your hoping for quite a bit at these distances but you never know until you try.
