(at around 56 mins) Doyle fires his gun three times to kill four infected men. However, at the third shot, two of them fall, but since they weren't lined, it would be impossible to kill both men with only one shot.
Many times, the actual sounds of the Aerospatiale Gazelle are replaced by a more familiar helicopter sound, although in a few places, you do hear the Gazelle's distinctive high rotor speed and squealing from the Fenestron tail rotor.
General Stone says that the Infection does not "cross species." However, the original outbreak began when humans came in contact with infected chimps. This is most likely caused by a confusion between Order and Species. The Rage virus can infect all species within the primate order, but it cannot infect any other order (aquatic life forms for example).
Right after the virus breaks out again and the medical officer grabs the two kids from isolation she is trying to get them out of the building when a soldier stops them. The soldier keeps calling her "sir" when in fact female officers in the US armed forces are addressed as "ma'am" by those of lesser rank, not "sir".
While trying to escape with the survivors, Scarlett is shot on the inside-front of her left leg, which she bandages up. Later in the abandoned fairground/park she re-bandages her wound and it has moved to the outside-front of the leg.
Flynn's helicopter changes multiple times. He falls asleep in an Aerospatiale Gazelle. When he attempts to rescue Doyle, he is flying an Aerospatiale A-Star. When he lands in the stadium to rescue Doyle and the children, he is once again flying an Aerospatiale Gazelle.
(at around 30 mins) There is a group of infected people attacking a car with people inside, (at around 37 mins) there is a shot of the car with no people around it. Despite the smoke, there were infected people ahead of the car, and we should see them.
When the aircraft with repatriated people approaches London, it is headed to Runway 09 at London City Airport. When the passengers get off the aircraft, they are at Stansted Airport, in the terminal buildings.
Flynn's helicopter is a British Gazelle. The US force could have taken control of it after arriving, but considering the state of the country, and the fact that the US uses their own equipment when possible, it's not likely.
After repeated attempts to start the car using the starter, Doyle decides to push-start the car to help Andy, Scarlet and Tammy escape the gas. Push-starting only works when the battery doesn't have enough power to activate the starter. Since the starter was working, push-starting would be useless.
When Andy & Tam escape to re-visit their old home, they are shown crossing Tower Bridge, which as they have started their journey from the Isle of Dogs, means they are travelling South across the river, but the next shot shows them passing the 'London Gherkin', which is built on the former site of the Baltic Exchange, St Mary Axe, in the City of London, on the North Bank.
The 'Air Cavalry' firebomb London when the infected break out. They are shown operating fighter jets, but actual Air Cavalry are ground forces transported via helicopters, and would not have been tasked with bombing a city. The Air *Force* operates jets and would have been the ones responsible for the bombing.
When the children are riding the motorbike through the cemetery, fresh flowers are on one of the graves. Since the cemetery is outside the quarantine zone, there should be no-one around to visit the deceased.
On Doyle's M4 he has an EOTech and a PVS-14 NVG night vision scope. Whenever it shows him looking down the sight he has the standard cross hair, when in fact the EOTech would be a red ring with a dot in the middle.
SPOILER:(at around 1h 16 mins) When the helicopter is chopping the people to bits, just after Sam falls from the chopper, a soldier with his right arm and most of his torso blown away is seen casually walking away from the camera for about four seconds.
After code red is called, aircraft come in to firebomb Canary Wharf. They lay down carpets of fire in the streets, but the light from the flames is not reflected in the huge number of windows in the buildings which line these streets.