(CNN) — It's been another turbulent year for aviation.
As we end 2021, the thousands of holiday flights canceled due to the rampaging Omicron variant is delivering another hammering to an industry that's struggling with lost revenue, disruptive passengers, and being at the front line of both interpreting and enforcing governments' Covid regulations.
Here we look back at how CNN covered the biggest developments in aviation in the past 12 months.
Vaccine passports and mandates
It's hard to believe, but it's barely been a year since the UK's Margaret Keenan became in December 2020 the first person in the world to receive a Covid-19 vaccine. Today, more than eight billion have been administered. The airline industry has had to adapt fast. While now we're getting used to all the digital documentation we need in order to fly, it was only in January that the United States introduced Covid testing and CNN was speculating on the ethics and practicality of introducing "vaccine passports." Attitudes to vaccine mandates for airline staff varied around the world, proving particularly contentious in the US, where Delta Air Lines and Southwest held out on making them compulsory for their workers. Dr Anthony Fauci, top medical adviser to the White House, said in September that he supported a mandate for passengers too, but the travel industry was not on board and this remains a relatively uncommon measure worldwide. In October, Air New Zealand became one of the highest-profile airlines to announce a passenger mandate, which it will put into practice in February 2022.
The front line of enforcement
Net industry losses for 2021 are expected to be close to $52 billion, but on top of these financial woes, the job was only getting tougher for those airline workers responsible for ferrying us through the skies.
Flight attendants are getting self-defense training as the number of unruly passengers is on the rise. CNN's Pete Muntean reports.
As well as battling with passengers who don't want to wear masks or who try to drink their own alcohol in-flight, airlines have had to keep up with fast-changing and often confusing Covid legislation introduced by governments.
In April, an Australian domestic flight was delayed so long quarantine rules changed while passengers were mid-air, while in December, Ghana's international airport introduced some of Africa's toughest regulations, fining airlines $3,500 for every unvaccinated passenger they flew into the country.
Busy planes and rising fares
Cancellations, packed planes and ever increasing fares have become the "new normal" for US air travel, CNN wrote in November. Operational meltdowns at Southwest and American Airlines were behind the recent cancellation of thousands of flights, but staffing shortages were also leading to overworked flight crews, while less choice in flights was leading to more expensive tickets.
One small upside for consumers in the Covid era is that globally many airlines have introduced and retained much greater flexibility when it comes to changing flights at short notice. However, flying is now often a stressful and expensive experience overall -- not helped by "fit to fly" Covid testing still being a Wild West of private companies offering hugely varying levels of service and value for money.
Hellos, goodbyes and seeya laters
CNN's Richard Quest boards JetBlue Airlines first transatlantic flight and discusses the travel challenges JetBlue CEO Robin Hayes dealt with ahead of the New York to London route's launch.
In February, Bombardier announced that it was ceasing production of the iconic Learjet plane, the small private jet plane that was for decades synonymous with high-end business travel. At the opposite end of the size scale, the last ever Airbus A380 -- the world's largest passenger airline -- was delivered to its customer airline Emirates in December. A380s, and scores of other planes, continued to be kept in storage by airlines due to lack of pandemic demand, although many reemerged as travel increased during the summer season. In the California desert, there was even a problem with parked-up A380s attracting rattlesnakes. And in China, the long-awaited Chengdu Tianfu International Airport opened in China. Constructed at a cost of about $10.8 billion, phase one of the mega-hub has the capacity to handle up to 60 million passengers per year.
The Belarus 'hijacking'
Willie Walsh, the director general of the International Air Transport Association (IATA), tells CNN's Becky Anderson that the diverted Ryanair flight was an "extremely dangerous action."
In May, Ryanair flight FR4978 from Athens to Vilnius was forcibly diverted to Minsk, escorted by Belarusian fighter jets, in order for Belarusian authorities to arrest opposition activist Roman Protasevich and his Russian companion Sofia Sapega.
Three days after the incident, European airlines were formally stopped from flying over Belarusian airspace, effectively redrawing Europe's air map.
The carbon question
At its annual meeting in October, the International Air Transport Association (IATA), rubber-stamped a resolution in support of net-zero carbon emissions by 2050.
With the focus on climate change during the COP26 summit in Scotland in November, CNN produced this long read on how close we are to guilt-free flying becoming a reality. We also kept up with the latest developments in low-carbon alternative air travel, such as helium-fueled airships for inter-city trips. Carbon-chugging pleasure trips were not by any means off the agenda in 2021, though. "Flights to nowhere" -- round-trip sightseeing tours -- were a fad, particularly in Asia-Pacific. A Qantas trip to see the supermoon and full lunar eclipse 40,000 feet above Australia sold out in May in 2.5 minutes.
The supersonic dream hit turbulence
The long-held dream of a successor to Concorde became a little more distant when Aerion, one of the major players in the race to build a supersonic passenger jet, collapsed in May after running out of cash. It had been just months since it had announced grand plans for a fancy new global HQ to produce its family of jets. Colorado-based Boom Supersonic, meanwhile, is pressing ahead with its plans to get the 1:3 scale prototype aircraft of its Overture jet up in the air. Its ambitions remain lofty: CEO Blake Scholl told CNN in May that the company's aim was to "fly anywhere in the world in four hours for $100." Atlanta-based Hermeus is working on an even-faster hypersonic passenger jet -- that means speeds of Mach 5, or five times the speed of sound. That'd get an aircraft from New York to London in just 90 minutes, making Concorde's three hours look sluggish.
Looking towards 2022 and beyond, first class is disappearing from many airlines, with business class options instead becoming more luxurious.