Rookie co-pilot Scott faces his worst nightmare when a faltering Curtiss C-46 Commando engine and low fog force a scary landing. Ambitious young flyer Alex must prove himself when Buffalo's chief pilot gives him control of the 20-ton Douglas DC-4 for the very first time. And boss' son Mikey gets in hot water when "Buffalo" Joe needs the backup Douglas DC-3 – and it's nowhere near ready.

Christmas is just around the corner, but Buffalo's crucial food and mail runs come to a halt. An engine seizure strands Scott, AJ and the C-46 plane, creating a chaotic chain reaction. Crusty mechanic Chuck must attempt a bare-handed engine swap in minus 30, and pressure from customers and co-workers pushes cargo manager Kelly to the breaking point.

A string of bad luck turns chief pilot Arnie's 66th birthday run into the flight from hell – and threatens to spoil his naughty birthday surprise. Ramp hand Jeremy is desperate to move up the ranks, but a female newbie could throw a wrench in his plans. And after the crew works all night to turn the DC-4 into a flying gas tanker, new co-pilot Alex flies a tricky fuel haul.

When a power failure leaves Rankin Inlet exposed to the brutal northern elements, captain Justin races to deliver an emergency generator. Ramp hand Jeremy tries to move ahead of co-worker Audrey by training a new hire from India to replace him. And when the recession nips at Joe's heels, he tries to broker a $7-million deal that could save Buffalo's hide.

Mechanic Cory races against the clock to turn two short-haul waterbombers into trans-Atlantic aircraft for the epic journey to Turkey. It's up to engineer Adam to get the C-46 crew out of a jam on a remote airstrip in minus 40. And when captain Devan and co-pilot Scott encounter the menace of wind shear at notorious Bear Rock, it's a hair-raising experience that tests their friendship.

A charter flight falls through the cracks after the McBryans attend a wild family wedding, and an irate Joe pulls captain Justin from the Turkey test flights to do the job. Justin's task is to move an impatient Brit, his dog and all his worldly possessions to a remote northern outpost, but the weather isn't cooperating. Meanwhile, Devan ponders a job offer in Africa - leaving girlfriend Jynelle to ponder their future.

A furious Joe fights against a federal suspension that will prevent him from carrying passengers for the first time in 20 years. It's also a setback for Jeremy and the other rampies, which takes a turn for the worse with an unexpected injury. For the Turkey waterbomber team it's finally a go. Arnie, Justin and the crew set off on the first leg of their journey, a risky trip across Canada in the dead of winter, with no de-icing equipment.

AJ and Candace get married in the Ice Castle. A frustrated Chuck tries to get the Electra to pay her way. A flummoxed Mikey tries to bake a cake for Joe's birthday. And in Newfoundland, a fuel leak, a sobering survival course and a tragic crash rattle the Turkey crew.

The Turkey crew makes the critical jump over the North Atlantic. But en route to Portugal, one crew is forced to turn back. With no power on one engine and no way to maintain altitude, they must get back into Santa Maria, where the airport is on full emergency alert. And Mikey and Scott search for a new rampie, while Jeremy's hopes plummet even further.

Joe gets a lucrative late-season contract to fly mining equipment to an airstrip on a frozen lake, sending C-46 and DC-4 crews on a race against the spring melt. But conflict erupts between Devan and a senior pilot. And when the client reports an on-site incident, Joe goes on the warpath. Though Jeremy has missed a number of flight attendant classes, he's confident he can catch up to fellow rampies Audrey and Wilf. But too much confidence just may be a dangerous thing. And over the North Atlantic, Arnie, Justin and Cory press on to Turkey, even though they have only half of the spare parts in their plane. But there are some serious volcanoes and busy Mediterranean air traffic ahead.

Across the world in spectacular Izmir, after thousands of hours of painstaking preparation and life-risking flying, a terrible accident devastates the Turkey crew - and everyone at Buffalo Airways. In Yellowknife, the spring melt is well underway, and northerners are finding ways to celebrate, from checking out the melting waterfalls to racing jet boats onto the remaining river ice. It's also Wilf's first run as flight attendant on the DC-3 - for which he insists on wearing a shirt and tie to the consternation of the entire company. It's the final push Jeremy needs to move to HQ in Yellowknife. Kelly and Jynelle dig up a house-warming surprise that practically brings tears to the gruff rampie's eyes.

Cargo manager (and unofficial Buffalo den mother) Kelly has problems enough when Jynelle's holiday leaves her shorthanded. But when her engineer husband Juan quits on the spot after a blowout with Joe, Kelly is left in a terrible position. Will Kelly stay - or will she go? Scott also gets bad news: he must stand down from flying so a rival co-pilot can be fast-tracked to captain. Scott pulls out all the stops to secure a new contract flying practically to the North Pole, which will get him back in the pilot's seat. But his rival is also interested in this new dream job - flying the C-46 to Eureka, a tiny research station at the top of the world. And after nine months of brutal work and tough luck, Jeremy sees light at the end of the tunnel. Buffalo needs a new DC-3 co-pilot, and contrary to expectation, he's getting a crack at it. But first, he's got to pass the test of flying with Joe.

After her husband's acrimonious departure from Buffalo, Kelly has a confrontation that decides whether she, too, will quit. Jeremy makes a mistake that could end his Buffalo career. An aviation gas shortage brings a sobering dose of reality to the McBryans. And after a visit from his mom, fate throws Scott an unexpected curve ball. When the dust settles, someone will be leaving Buffalo Airways.