IFR en route high-altitude charts
IFR (instrument flight rules) en route high-altitude charts
En route high-altitude charts are designed for navigation at or above 18,000 ft MSL (mean sea level). This four-color chart series includes the jet route structure; very high frequency navigational aids (VHF NAVAIDs) with frequency [only high and low VORs (very high frequency omnidirectional radio-range) and not terminal VORs], identification, channel, and geographic coordinates; selected airports; and reporting points. Scales vary from 1 in = 45 NM (nautical miles) to 1 in = 18 NM; 55 × 20 in can be folded to 5 × 10 in. It is revised every fifty-six days in the United States (see page 353).