If you're in normal physical condition it should be no problem to get up there. For people with circulation or heart problems it might be helpful to visit a doctor before.
I've been in Axalp for two times and I really suggest to find an accommodation in the village Axalp itself.
But you have to be quick. Reserve a room as soon as possible. More infos about hotels etc. are available at
http://www.axalp.ch" onclick="window.open(this.href);return false;
The advantage of being in Axalp already is saving time in the morning. No driving, no time wasted while looking for a parking space etc.!
From Axalp it will take you round about 1-2 hours to walk up to the viewing area. But there is also a lift running from Axalp with which you can save some of the distance. Although it isn't the distance. Axalp is situated ca. 1500m above main sea level, the viewing area is in ca. 2300m.
You can go up there the whole week. The firing practice normally starts around 0900 CET so it is a good idea to start your walk around 0600 as the ways up there will be closed during the firing practices. Firing might take place between 0900-1130 and 1400-1630. On Monday and Tuesday of that week you might also see training flights for the official demo e.g. Hornet Display, Patrouille Suisse etc.!
The official Axalp Demo takes place on Wednesday and Thursday starting at 1400 each day. In the morning hours normal shooting will take place.
If on one of these days the show has to be cancelled due to weather the Friday will see a demo. The F-5 and F-18 normally operate from Meiringen, the PS from Emmen.
As the show takes place in October it might be winter already so bring appropriate clothing with you. The weather can change very quickly up there. Always have some fresh clothes in your bagpack. When you arrive up there you should change your sweated shirt and trouser etc.! It can be very cold and windy up there.
When the sun comes out later on it is getting better.
Apropos weather. Be warned. You might be up there and the sun is shining but you don't see a jet at all because the jets at Meiringen can't take off due to fog. It can also be the other way round. Quite good conditions but the range is in the clouds or fog and once again no activities up there.
The worst scenario: The weather is a total mess up the whole week and you might see no jets up there at all.
But no risk no fun. So far it was always worth it.