What is the minimum VFR flight visibility?

Where pattern altitude puts you

Leadville's field elevation is 9,934 feet. A pattern 1,000 feet above the field puts you at about 10,934 feet MSL. The airspace at Leadville is Class G at the surface, with Class E starting 700 feet above the ground around the airport. At pattern altitude, you're in Class E.

Class E at or above 10,000 feet

14 CFR 91.155(a) gives Class E two sets of minimums, split at 10,000 feet MSL:

• Below 10,000 MSL: 3 statute miles visibility, 500 feet below, 1,000 feet above and 2,000 feet horizontal from clouds.
• At or above 10,000 MSL: 5 statute miles visibility, 1,000 feet below, 1,000 feet above and 1 statute mile horizontal from clouds.

At 10,934 feet you're above the threshold, so you need 5 statute miles.

Why 3 sm is so tempting

Three statute miles is the Class E minimum at most airports, because most traffic patterns sit below 10,000 MSL. Leadville is high enough that its pattern crosses the threshold.

Statute miles, not nautical

The visibility minimums in 91.155 are all in statute miles. An answer in nautical miles doesn't match any VFR weather minimum.

Why the floor of Class E matters

Class E at Leadville starts 700 feet above the ground, so the pattern is in Class E. If it started at 1,200 feet instead, a pattern 1,000 feet above the field would be in Class G, where the daytime minimum within 1,200 feet of the surface is 1 statute mile and clear of clouds. Check the sectional for where Class E begins before you decide which minimums apply.