** Shares of delivery firm United Parcel Service UPS.N down 3.3% at $92.70, Fedex FDX.N down 1.8% at $257.30

** FAA prohibited MD-11 planes from flying on Saturday after a crash of a UPS cargo freighter killed at least 14 people in Kentucky

** UPS has grounded 26 aircraft, or about 9% of its fleet, and FDX has grounded 28 aircraft, or 4%, from a 700-strong fleet

** Boeing BA.N says it supports the FAA order

** Including session's moves, UPS shares down 26.5% and FDX shares down 8.5% YTD

(Reporting by Megavarshini G. Somasundaram in Bengaluru)

((Megavarshini.SomasundaramGnanasundari@thomsonreuters.com))