At the height of the global pandemic, the skies were <a href="https://www.thenationalnews.com/lifestyle/travel/we-have-the-entire-sky-to-ourselves-what-it-s-like-to-be-a-pilot-during-the-pandemic-1.1017487" target="_blank">eerily empty</a> as the world battened down the hatches to tackle the coronavirus pandemic. Countries <a href="https://www.thenationalnews.com/lifestyle/travel/coronavirus-emirates-airline-to-suspend-most-passenger-flights-1.990911" target="_blank">closed their borders</a> to travellers and airlines grounded jets as rising Covid-19 cases obliterated travel demand. In April last year, more than 16,000 jets were grounded worldwide, reported aviation data provider Cirium. As well as bringing the aviation industry to its knees in what the International Air Transport Association called the industry’s <a href="https://www.thenationalnews.com/business/aviation/100-days-of-coronavirus-how-covid-19-has-affected-the-travel-industry-and-what-lies-ahead-1.1003008" target="_blank">“darkest hour”</a>, the pandemic also brought new challenges for airlines that suddenly had thousands of planes parked nose to tail or wingtip to wingtip on the tarmac. Fast forward to today as Covid-19 related travel restrictions in many destinations begin to ease and the demand for air travel is picking up again. Domestic flights are leading this recovery, and are expected to reach 93 per cent of pre-crisis levels next year, according to the latest figures from<a href="https://www.thenationalnews.com/business/2021/10/04/iata-agm-global-airlines-expect-narrower-losses-in-2022-amid-uneven-pandemic-recovery/" target="_blank"> Iata</a>. And while international travel continues to lag behind due to border restrictions and complex testing rules, these figures are also on the up with the association expecting it to reach 44 per cent of pre-pandemic levels in 2022. While this return to service has been patiently and eagerly awaited by the world's airlines, its arrival is not without its challenges. Now, thousands of aircraft, some of which have not flown in many months, must be readied to take to the sky again. In June, the European Union Aviation Safety Agency issued a directive covering the Airbus A320 family stating that "an increasing number of operational disruptions have been reported due to airspeed discrepancies" as they return to the air. Boeing also previously said extensive preparations must be carried out to return jets to service from long-term storage. In the UAE, <a href="https://www.thenationalnews.com/lifestyle/travel/how-covid-19-changed-the-skies-charting-the-pandemic-s-effect-on-travel-one-year-after-the-uae-first-paused-flights-1.1167806" target="_blank">a major world hub for air travel,</a> Etihad Airways was one of the airlines majorly affected by the global pandemic. The Abu Dhabi airline was forced to ground the majority of its fleet when the UAE closed its airspace to help limit the spread of Covid-19, back in April 2020. When this initial flight ban was lifted, the national airline of the UAE, like so many other airlines around the world, had to keep many of its jets on the ground as there was simply too little demand for commercial air travel. But with the UAE having recently <a href="" target="_blank">eased entry restrictions</a> amid higher vaccination rates around the world, Etihad is preparing for its return. The airline has reported a hike in demand for travel since Abu Dhabi removed quarantine restrictions for vaccinated passengers and ticket sales for the coming festive period show a thirst for travel. “As travel markets are reopening quickly and consumer confidence is growing rapidly, Etihad is seeing pent-up travel demand drive an increase in bookings. In particular, as Abu Dhabi announced the welcoming of fully vaccinated passengers without quarantine, we saw an increase in bookings to and from the UAE, and this was a very welcome move," said Martin Drew, senior vice president of sales and cargo at Etihad. “Since the pandemic, we’ve introduced a more agile and flexible approach to network planning, allowing us to react when country borders reopen. Being a mid-sized carrier, we have the opportunity to do this, and it’s an opportunity we’re taking advantage of." To keep up with these <a href="https://www.thenationalnews.com/travel/news/2021/10/31/etihad-resumes-flights-to-madinah-in-saudi-arabia-after-19-month-suspension/" target="_blank">route restarts</a>, Etihad must ensure it has enough aircraft ready to fulfill passenger demand. The airline is working to put more of its grounded fleet back in the air and the preparation is taking place at Etihad Airways Engineering, a sprawling purpose-built facility located close to Abu Dhabi International Airport. “This aircraft right here is an Airbus A320 aircraft, and it has been parked for the last three months,” explains Rami Awadalla, director of fleet engineering at Etihad, when we join him at the facility. “We’re actually bringing it back to service and this is why it’s now here in our maintenance facility.” When a multimillion-dollar aircraft hasn’t operated in some time, making it fly again is not quite as simple as turning on the engine. Instead, this narrow-body is being put through its paces by a highly specialised crew of engineers and technicians. Having been parked on the ground for more than three months, the Airbus must undergo a series of checks and pass several inspections before it can fly again. These include airworthiness checks, routine maintenance, cabin inspections, cleaning processes and a complete cabin sanitisation. And all of this happens on top of ongoing maintenance that took place while the jet was idle. “Unlike with cars where you can simply park it and mostly forget about it, with an aircraft you need to continuously maintain it if it’s parked, or even when it's stored,” says Abdwalla. Parked jets receive regular attention with accumulated water being drained every week and mechanical parts, such as the landing gear, having to be routinely lubricated. There's also inspections on things like the engine inlets to ensure that they are protected from corrosion and rust build up. These planes also need shelter from weather elements, something that is achieved by <a href="https://www.thenationalnews.com/lifestyle/travel/all-wrapped-up-how-emirates-is-keeping-its-parked-jets-safe-1.1013126" target="_blank">wrapping the aircraft </a>to shield it from things like sand and dirt which can cause further damage. Wrapping helps protect against humidity, which averages around 60 per cent in the Abu Dhabi desert. These measures also help prevent birds and insects from finding their way into the aircraft. On top of the regular checks, every time a parked jet is being brought back into service, Etihad drafts in a team of up to 20 experts to run through an in-depth maintenance programme, something that can take up to 24 hours for each aircraft. “We start by cleaning the aircraft’s exterior so it allows us to inform the inspection clearly and this is then followed by powering up the aircraft and performing some of the important tests and functional checks,” says Abdwalla. “These can range from checking flight controls, to the instrumentation on the aircraft and all the way up to the engines where we run them to make sure they perform correctly.” Flight Controls is a critical aircraft system which is responsible for managing the aircraft’s stability and maneuvering on a pilot’s commands during a flight. As part of the system check-up, engineers test the flight control surfaces to ensure there is no obstruction and that the hydraulically-powered actuators operate effectively. The static air pressure sensor, used to indicate the aircraft’s altitude on the pilot’s instruments, also needs to be tested. These sensors are sealed off when the aircraft is parked so they need to undergo a full inspection before the jet is cleared to fly again. Making sure each aircraft is also ready to welcome passengers is another part of the process. “We initially do a very detailed clean that involves clean-up of the seats, carpets, overhead bins and all the areas in the cabin. After that we perform a full functional check of the cabin using the technical team, making sure that all the in-flight systems and all the seats function correctly.” Other areas and facilities including the bathrooms, galley, coffee makers, ovens and food chillers are also tested to ensure they still function correctly. Technical teams replace or repair any parts of the jet that have been damaged or broken while it's been on the ground. When the team is satisfied that the aircraft is in perfect working order, Etihad santisies the cabin as part of its <a href="https://www.thenationalnews.com/lifestyle/travel/etihad-introduces-in-flight-wellness-ambassadors-to-give-travellers-peace-of-mind-1.1027271" target="_blank">wellness campaign</a> which has been introduced to protect travellers flying during the global pandemic. “We then perform the cabin santisation, which involves a complete wipe down of all touch point areas in the cabin and, at the end, we perform a fogging of the cabin … spraying a mist that covers all the air with a sanitisation product,” explains Abdwalla. With the final process complete, the narrow-body is ready to return to Etihad's operating fleet and carry passengers on their travels once more. “As we see a ramp up of operations around the world, with countries opening up their borders, we are bringing more aircraft back into service,” says Abdwalla, who is gearing up for a busy last few months of 2021.