Exhibit 5.1



                                                   January 27, 1998



Securities and Exchange Commission
450 Fifth Street, N.W.
Washington, D.C.  20549

            Re:         FDX Corporation

Dear Sirs:

            I am an executive vice president, secretary and the general counsel
of FDX Corporation, a Delaware corporation ("FDX"). This opinion is issued in
connection with the registration on Registration Statement Form S-8 of the
shares (the "Shares") of common stock, par value $0.10 per share, of FDX
Corporation, which will be issued under the FDX adjustment program to the
holders of awards ("Awards") under certain benefit plans of Caliber System, Inc.
("Caliber") pursuant to the Agreement and Plan of Merger dated as of October 5,
1997, (the "Merger Agreement") among Federal Express Corporation, FDX, Caliber,
Tires Merger Sub Inc. and Fast Merger Sub Inc.

            I have examined originals or copies, certified or otherwise
identified to my satisfaction, of such documents, corporate records,
certificates and other instruments, and have conducted such other investigations
of fact and law, as I have deemed necessary or advisable for the purpose of
rendering this opinion.

            Based upon the foregoing, I am of the opinion that the Shares to be
issued under each Award have been duly authorized and, when issued in accordance
with the terms and conditions of the Merger Agreement and the relevant documents
relating to each such Award, will be validly issued, fully paid and
non-assessable.

            I hereby consent to the use of this opinion as Exhibit 5.1 to the
Registration Statement referred to above.

            I am a member of the Bar of the State of Tennessee and the foregoing
opinion is limited to the laws of the State of Tennessee, the federal laws of
the United States of America and the General Corporation Law of the State of
Delaware.

            This opinion is rendered solely to you in connection with the
Registration Statement referred to above. This opinion may not be relied upon by
you for any other purpose or relied upon by or furnished to any other person
without our prior written consent.

                                             Very truly yours,
                                             Kenneth R. Masterson
                                             Executive Vice President, General
                                             Counsel and Secretary