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Join Date: Sep 2009
Location: Minneapolis: DL DM charter 2.3MM
Programs: A3*Gold, SPG Plat, HyattDiamond, MarriottPP, LHW exAccess, ICI, Raffles Amb, NW PE MM, TWA Gold MM
Posts: 102,617
If the change is mainline to commuter carrier, you have the right to a full refund. However, if it's only a change of aircraft type, possibly with a change from one DL Connection carrier to another, I don't think DOT rules cover this.
As usual, figure out what you want, then call and ask nicely.