(Travel + Leisure) -- I thought I was being clever when I booked a $698 round-trip Delta flight from New York to London with the idea of getting an upgrade for 50,000 frequent-flier miles.
But when I went to the Delta website to complete the upgrade process, I was informed that I didn't qualify. I called a Delta agent to ask why.
"You bought a cheap ticket," the agent said. Turns out I had a T fare, which doesn't qualify for an upgrade. For that I would have had to buy a more expensive M, B, or Y economy fare, she said.
The agent was willing to rebook me at the cheapest price for an upgradable ticket: $2,393. On top of that I would have had to use 50,000 SkyMiles (worth $1,000 based on the commonly accepted value of 2 cents per mile), for a cash equivalent of $3,393.
Here's the kicker: I could have bought a business-class ticket on that same flight for only $2,800 -- $600 less than the upgrade would cost.
Frustrated as I was with Delta, this situation could have happened with any airline, as fare codes have become increasingly difficult to decipher.
So what are the restrictions? It depends on the carrier: American, Continental, and US Airways have little to no restrictions on economy fares; Delta and United have more rules.
Even with a qualifying airfare, you might find your flight has already reached its limit of upgrades ("capacity controlled," in airline-speak). And some qualifying tickets require higher co-pays (up to $500 each way) or more miles than others. The reason? Too many fliers with too many miles, thanks partly to credit-card and other non-air-travel promotions.
An alternate strategy would be to exchange miles for a business-class ticket rather than for an upgrade; it could be a better value.
But if you do decide to upgrade, you'll want to figure out the real cost (airfare plus miles plus co-pay) to decide if it's worth it.
You might find a good deal, especially on domestic flights. More likely, you'll be as surprised as I was to discover that, increasingly, upgrading with miles isn't the bargain it once was.
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