A dispute between Iowa Pacific Holdings and Amtrak has sidelined a Denver ski train that was scheduled to start service next week. Iowa Pacific owns the Rio Grande Scenic ski train and had negotiated with Amtrak for staffing, but a contract was never signed. Iowa Pacific is suing Amtrak. Union Pacific, which owns the tracks, gave exclusive approval to Amtrak to operate the train. More than 13,000 people have bought tickets through March.