Nos. 91-2995, 91-3335. Submitted February 12, 1992. Decided May 4, 1992. John F. Veldey, Marshalltown, Iowa, argued (John B. Grier, on brief), for petitioner Midland Transp. Co., Inc. Karen L. Arndt, Washington, D.C., argued (Paul J. Spielberg, Jerry M. Hunter, D. Randall Frye and Aileen A. Armstrong, on brief), for respondent N.L.R.B. Review of order of National Labor Relations Board. Before BOWMAN, WOLLMAN, Circuit Judges, and WOODS, District Judge. The HONORABLE HENRY WOODS, United States District