"complimentary upgrade" is a correct phrase and can be used in written English.
It refers to a free and more luxurious improvement or addition to something, such as a hotel room or airline seat. Example: The hotel manager informed us that we had been given a complimentary upgrade to a suite with a beautiful view of the city.
"Got a complimentary upgrade to first," the e-mail said.
Or, if you're really nice, they might give you a complimentary upgrade, with the hope that you'll return.
The source added that when Virgin staff spotted Corbyn sitting in a vestibule they offered him a complimentary upgrade to first class, which he refused.
He estimates that he gets a complimentary upgrade — arguably the most important benefit of elite status — on only 15 to 20 percent of his domestic flights, compared with 40 to 50 percent several years ago.
She and her owner got a complimentary upgrade to first class, where there is more room, and were seated in the first row, with Charlotte at her feet, on Oct. 17.
You get complimentary upgrade surprises from UberX to Uber Black and other high-end cars.
Travellers are also benefiting from complimentary upgrades that weren't available in the past.
It explained that this is how its system works for processing complimentary upgrades and that he would be refunded – which he was eventually.
"Delta SkyMiles offers program amenities frequent fliers want most, like a first-class cabin, unlimited complimentary upgrades and a robust international network," said Chris Kelly Singley, the general manager for corporate communications at Delta Air Lines.
This is usually the time of year when frequent fliers who earned elite status in the previous year can stop obsessing about qualifying miles and enjoy the fruits of all their travels: complimentary upgrades.
The airline rarely gives complimentary upgrades.
