There actually seems to be several candidates to this title:
1) Vallée Blanche in Chamonix from Aiguille du Midi down to Chamonix. There are several different numbers given for this run between 20 and 22 km. The Chamonix home page claims 20 km. Note that this is not a piste, it's a commonly used off-piste route where a mountain guide should be used.
2) From Kleine Matterhorn to Zermatt. Ski-zermatt claims 13 km and zermatt home page claims 22 km.
3) The Sarenne run in Alpe d'Huez is often claimed as the longest piste. It's on the piste map (from the Alpe d'Huez home page) stated as 19 km but on the Alpe d'Huez home page itself it says 16 km so it's probably not the longest piste but it is the longest black piste, even though the last part of it is more transport than black.
2.5 miles (4.0 kilometer) is the longest run in Utah.
400 meters
The alternate angle of depression is the angle of elevation and so 51/tan(6.7) = 434 ft which will be the length of the ski run providing the given information forms a right angle triangle.
Vail is the biggest ski resort in Colorado with more than 5000 acres, and it's also the biggest ski resort in the United States. Winter Park is also a big ski resort in Colorado. A bit smaller than Vail, but maybe even more famous since it's the closest one to Denver. Telluride is another large ski resort. The longest run in this resort is 4.6 miles long!
ski's
Vikersund, which has the record for world's longest jump.
380 days
Mount Baker
Village Way. It starts at the top of the Panoramic lift and ends at the WP base area.
The longest run at okemo is Mountain Road. It is 4.5 Miles long Startin all the way at the top, and going all the way to the bottom.
The Brighton ski resort in Brighton, Utah is a pretty big complex. They have over one thousand acres of land, 66 ski runs, and one run is five miles long.
The longest ski pole to fit would lie diagonally. The length of the diagonal can be found by the pythagorean theorem.d=sqrt(1202+252)d ~= 122.58 cm