Originally Posted by JAXPax

Don't confuse UA "could not purchase that space for you" with "UA will not purchase that space for you." Several airlines in this country without FIM agreements, such as one where I worked, whipped out a credit card, went to southwest.com and clicked BUY. Or have something like an Orbitz for Business portal to do so, ensuring that it complies with certain limits (like not buying a First seat just because it's all that's left on a DL flight). United has chosen to limit its OA rebooking options.