This was meant to be mountain flight. We wanted to fly from Grenchen to Sion via Thun, Interlaken, Meiringen, Grimselpass, and Brig. In case the Grimselpass would not be opened we had planned an alternative route from Meiringen to Luzern.
Although the weather when we woke up was beautiful when we took off from Grenchen, we were in not very pleasant haze causing poor visibility, few to scattered clouds above us at 3500 to 4000 ft and gusty wind. It would have been probably better if we climbed above this haze, but our route was first below Bern TMA (5500ft), which I (in the retrospect - for no reason really) did not want to penetrate.
Once we reached Thun the visibility has increased (we also climbed to 4500ft). The views were spectacular. We flew along Thunsee, then over Interlaken and then along Brienzersee. As we approached the end of Brienzersee both Haslital (would lead us to Grimselpass) as well as the valley which goes to Luzern seemed to had not very good visibility and seemed narrower than we originally anticipated. This plus some eastern wind and my lack of experience in mountain flying lead us to the decision to turn back while it was still nice and trouble free.
On the way back we contacted Bern tower and got permission to cross Bern CTR (nice views over Bern). We approached Grenchen from west - runway 07 was in use so that would allow us nice and easy straight in approach.
Grenchen was very busy (much busier than on any other Saturday) because of Bueckers fly-in. Shortly before us 2 planes also coming from the west were asked to hold over Whiskey. We however were more lucky and flew straight in approach without any delays.
After landing and securing plane we looked at these Bueckers which already arrived, they were quite a few of them and new ones were still coming.
In summary although we did not fly the entire route we planned it was still very successful flight.