As the novel coronavirus continues to spread, commercial flights have all but stopped. The situation is so dire that the head of the trade group representing the world's airlines called the last few months "its deepest crisis ever."

A Reuters analysis of data from FlightAware, which tracks air traffic in real-time, reveals a series of sequential and precipitous declines in flights in four key regions as officials sought to contain the outbreak.

From March 24 to March 30, FlightAware tracked about 280,000 flights, down almost 500,000 from the same week a year earlier.

In late March, the International Air Transport Association estimated lost revenue from the coronavirus will exceed 250 billion U.S. dollars in 2020 and urged governments to offer immediate financial support to the industry.

The transport association said today's crisis is far worse and more widespread than after 9/11, when U.S. airlines lost approximately 19.6 billion U.S. dollars in revenue in 2001-2002. After the terrorist attacks, the U.S. government provided 15 billion U.S. dollars to airlines in compensation and loan guarantees.

Congress voted on March 27 to give the U.S. aviation industry 58 billion U.S. dollars in a coronavirus rescue package, and Singapore Airlines lined up a 13 billion U.S. dollars funding package led by state investor and majority stakeholder Temasek.

Airlines limit flights

Because of travel restrictions enacted by governments around the world, a rapidly growing number of airlines have grounded most or all of their fleets over the past few weeks or are doing so now.

In the Middle East, major carriers including Emirates, Flydubai and Saudia, Saudi Arabia's state airline, suspended all passenger flights. Israel's El Al slashed its flight schedule, and Turkish Airlines suspended all international flights on March 27.

In Asia, Singapore Airlines grounded most of its fleet on March 23 after the city state banned all short-term visitors, and Qantas suspended international flights until at least May after the Australian government banned the arrival of non-citizens and non-residents.

In Europe, passenger data from the region's Airports Council International reveals an even deeper industry crisis than air traffic statistics indicate. As of March 22, the number of passengers traveling into and out of European airports had declined by 88 percent, or 5.2 million fewer daily travelers compared to a year earlier.

In Italy, containment efforts to staunch the spread of the virus triggered a rapid drop. There, data shows a 98 percent decline in passenger travel, or 440,000 fewer daily passengers compared to the same time last year.

Budget airlines Ryanair and easyJet grounded most of their fleets in late March.

UK closes window

The number of passengers arriving to and departing from British airports has also declined, though at a slower pace than elsewhere in Europe. As of March 22, data shows passenger traffic down 82 percent from the same time last year.

One reason for the difference: The UK was originally exempt from the U.S. travel ban on foreign nationals who had recently visited China, Iran and a group of 14 European countries, said Michael Stanton-Geddes, head of economics at ACI-Europe.

The exemption "temporarily protected a lot of transatlantic traffic," he said. "People getting from Europe to the U.S. had to go through London."

As of mid-March, some vacationers were still leaving the UK for European destinations. On March 14, Jet2 turned around flights bound for Spain after the airline canceled all flights to the mainland.

In China, air traffic is starting to pick up after two months of severe travel restrictions. The country saw a half million fewer flights during the same two-month period compared to the same period a year ago.

Cargo supplants passengers

So far, the number of cargo flights has remained largely unaffected by the travel restrictions. 

Data from FlightAware shows flights by freight and package carriers such as Atlas, Polar, FedEx and UPS arriving in and departing from the United States initially declined during the first week of February 2020. The drop, which correlated to the Hubei Province lockdown, "shows how important China is to the world of international commerce," said Andrew Charlton, an industry analyst.

Shortly thereafter, however, U.S. cargo flights rebounded to previous levels, the data shows. 

Because passenger jets transport about half of all air cargo carried worldwide, the grounding of those planes has increased demand for freighters. In response, some commercial airlines such as American, Delta and Virgin Atlantic are using passenger jets solely for shipping cargo.