Minimum crossing altitude

Minimum crossing altitude (MCA)
Minimum descent altitude (MDA)
Minimum descent altitude (MDA) - 14 CFR 1.1 ...

Minimum crossing altitude (MCA). The lowest allowed altitude at certain fixes an aircraft must cross when proceeding in the direction of a higher minimum en route altitude (MEA).

Minimum Crossing altitudes are noted by X-flag with restriction.
MOCAs are preceded with an asterisk.
ORTOCAs by NOS or MORAs by Jeppesen or off-route obstruction clearance altitudes are now being included on en route charts.

Now, suppose you're six miles from a fix and 1,500 feet above its minimum crossing altitude. You know that it will take approximately three minutes to cross that fix at 120 knots (that's 2 miles of travel per minute).

See also: Locator, Direct, Obstruction, Obstacle, Air traffic