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                                                                    EXHIBIT 99.1
 
                             SOUTHWEST BANKS, INC.
                           900 GOODLETTE ROAD, NORTH
                             NAPLES, FLORIDA 33940
 
   THIS PROXY IS SOLICITED ON BEHALF OF THE BOARD OF DIRECTORS FOR USE AT THE
                        SPECIAL MEETING OF SHAREHOLDERS
 
    The undersigned shareholder(s) of the $.10 par value Common Stock of
Southwest Banks, Inc. ("Southwest"), hereby appoints and constitutes Gary L.
Tice and Garrett S. Richter, or either of them, to act as lawful attorney and
proxy of the undersigned, with the power of substitution for and in the name,
place and stead of the undersigned, to vote at the Special Meeting of
Shareholders of Southwest to be held on Monday, June 17, 1996, at the Naples
Beach Hotel & Golf Club, Naples, Florida at 5:00 p.m. (local time), or any
adjournment thereof, for the following purposes and upon any other matters that
may come before the meeting or any adjournment thereof, with all the powers the
undersigned would possess if personally present, hereby revoking all previous
proxies:
 
    1. To approve and adopt the Agreement and Plan of Merger by and among
       Southwest, F.N.B. Corporation and Southwest Affiliation Corporation, as
       set forth in Appendix A attached to the proxy statement.
 
       / /  FOR              / /  AGAINST              / /  ABSTAIN
 
    2. Unless indicated to the contrary below, the Proxies are authorized to
       vote, in their discretion, upon other business as may properly be brought
       before the meeting or any adjournment thereof. (Instruction: To withhold
       authority of the Proxies to vote for adjournment, including adjournment
       for the purpose of resoliciting additional votes in order to approve the
       proposed merger, check the following box.)  / /
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                  (Continued and to be signed on reverse side)
   2
 
                          (Continued from other side)
 
    THIS PROXY, WHEN PROPERLY EXECUTED, WILL BE VOTED IN THE MANNER DIRECTED
HEREIN BY THE UNDERSIGNED SHAREHOLDER(S). IF NO DIRECTION IS MADE, THIS PROXY
WILL BE VOTED FOR PROPOSAL 1.
 
                                              ----------------------------------
                                                          SIGNATURE
 
                                              ----------------------------------
                                                          SIGNATURE
 
                                              Dated: , 1996
 
                                              (Please date and sign exactly as
                                              name(s) appears on mailing label.
                                              When signing as an attorney,
                                              administrator, trustee or
                                              guardian, please give full title
                                              as such. If a corporation, please
                                              sign in full corporate name by
                                              President or other authorized
                                              officer. If a partnership, please
                                              sign in partnership name by
                                              authorized person. For joint
                                              accounts, each joint owner should
                                              sign.)
 
 PLEASE SIGN, DATE AND MAIL THIS PROXY PROMPTLY IN THE ENCLOSED REPLY ENVELOPE
            WHICH REQUIRES NO POSTAGE IF MAILED IN THE UNITED STATES