The recovery in Europe’s air traffic has hit a new milestone as people take to the skies again for summer vacations.

Aside from a brief pickup around Christmas, Europe’s air traffic is at its highest compared with pre-Covid levels since March last year, when the continent’s lockdowns really began to affect demand. On Sunday it rose just above 50% of 2019 levels based on a seven-day moving average, data from Eurocontrol show.

The revival offers some hope to the continent’s airlines, but also its oil refiners who’ve seen demand for aviation fuel collapse. The pandemic-driven slump in flying saw them divert production of normally valuable jet fuel into other oil products, like diesel and naphtha. Jet fuel’s price differential to diesel—an important metric for traders—has been slowly recovering from the lows of 2020.

In April, consumption of jet fuel and kerosene in OECD Europe was 690,000 barrels a day, according to the International Energy Agency. That’s an increase of 74% compared with a year earlier.

Europe’s air traffic has generally been on an upward trend since about mid-May, according to data from Eurocontrol. There could also be an influx of tourists from America in the coming months, with the EU lifting travel restrictions for U.S. residents.

Still, there’s a long way to go for Europe’s flight numbers. Even in Eurocontrol’s most-optimistic scenario, the continent’s air traffic is only set to reach 79% of 2019 levels by the end of this year. In the U.K.—home to many travelers to mainland Europe—the government’s decision to keep in place tight travel restrictions is widening a rift between airlines and health authorities.

“Demand is still well off pre-Covid highs and this is likely to be the case for years as international travel remains depressed,” said Jonathan Leitch, an oil market analyst at Turner, Mason & Co.