i. IFR (instrument flight rules). A ceiling less than 1000 ft and/or visibility less than 3 miles. A hatched area outlined by a smooth line.
ii. MVFR (marginal visual flight rules). A ceiling 1000 to 3000 ft inclusive and/or visibility 3 to 5 miles inclusive. A nonhatched area outlined by a smooth line.
iii. VFR (visual flight rules). No ceiling or a ceiling greater than 3000 ft and visibility greater than 5 miles. Not outlined.
These three categories are also explained in the lower right portion of the chart for quick reference.
An Illustrated Dictionary of Aviation Copyright © 2005 by The McGraw-Hill Companies, Inc. All rights reserved