Federal inmate Victor Barakat appeals from an order of the District Court 1 denying his 28 U.S.C. § 2241 petition in which he challenged a decision of the Bureau of Prisons to deny his request for a twelvemonth placement in a Residential Reentry Center (RRC). This appeal is moot, however, because Barakat was transferred to an RRC during the pendency of this appeal, and thus the court can no longer grant him the relief he requested. See Calderon v. Moore, 518 U.S. 149, 150, 116 S.Ct. 2066, 135 L.Ed.2d 453 (1996) (per curiam) (noting that when an event occurs during the pendency of an appeal that renders it impossible for the court to grant effective relief, the court should dismiss the appeal as moot). As for Barakat’s request that the remainder of his sentence be vacated, such relief is not available through a § 2241 petition. See Matheny v. Morrison, 307 F.3d 709, 711 (8th Cir. 2002) (noting that while a prisoner may attack the execution of his sentence in a § 2241 petition in the district of incarceration, a challenge to the validity of the underlying sentence is properly raised in motion under 28 U.S.C. § 2255 in the district of the sentencing court). Accordingly, we dismiss this appeal.