Airliner pitot tubes provide redundant inputs for indicated airspeed and altitude readouts as well as inputs to all the various computer systems used for flight management. GPS provides groundspeed and GPS altitude information independent of pitot tubes. Angle of attack vanes provide angle of attack information (AOA) - a plane will not stall/spin if it is flying at less than stall angle of attack. As a retired Navy carrier pilot who used AOA exclusively for carrier approaches and didn't even scan airspeed except for a crosscheck at the beginning of an approach, I have always questioned why airline pilots aren't trained to use AOA and GPS speed readouts whenever any questions arise about pitot static systems reliability. AOA/GPS may not be accurate to the knot (groundspeed is a function of variable windspeed and direction) but they will both keep you comfortably within stall margin. Another mystery of life - why do folks who have no clue about aviation and aerodynamics feel qualified to display their ignorance on TV or in forums like this?
Angle of Attack. It would have saved the Air France flight had pilots been trained to it too. AOA is the only thing that matters regarding wing stall and insufficient lift. It’s been around longer than airspeed measure, too. I believe the Wright brothers did it with a piece of yarn compared to a mark though they had pusher props. Flight control computers use AOA at relatively low speeds and Mach at higher speeds. It’s time we stop teaching airspeed and teach AOA. AOA is consistent no matter the weight load or angle of bank. While not familiar with the 737, I’ll bet it had AOA.
As a active commercial pilot for a large airline and a retired military pilot (20+) year flying fighters I want to throw in my 2 cents. In every military aircraft I've flown there is a AOA (Angle of Attack) indicator. Most commercial aircraft do not have this indication available to the pilot which shocked me when I started flying for the airlines. The data is provided to the flight computers but not displayed the the pilot in what I've experienced. If you lose airspeed indication then defaulting to the AOA indication will prevent you from entering a stall. Air France flight 447 that crashed into the Atlantic Ocean killing 228 passengers in 2009 could have been saved if the pilots had AOA indictions. Their pitot system experienced icing temporarily kicking off the automation. Inexperienced pilots put the jet in a full stall from 38,000' until impact. The FAA needs to mandate all air carriers have an AOA indication in the cockpit and ensure pilots are trained to use it. Secondly, many of these foreign carriers just don't have the quality of pilots we have here in the US coupled with the fact that there is a pilot shortage world-wide.
The account of the Air France tragedy that I read in Vanity Fair was rather damning for the captain (who did have a lot of experience). He apparently had spent the day golfing and perhaps partying a bit with his GF and seemed more intent on staying out of the cabin and trying to get rest during the turbulence--which did leave younger pilots in charge of the flight. I asked my now late father (10 years USN; 25 years Pan Am) before he passed if he thought 447 could have been saved. He sighed and said "if they [pilots] understood exactly what was going on". He further explained that hand flying a sweep wing jet is very difficult without reliable instrumentation or a visible horizon (447 was a redeye) and that the "coffin corner" (approaching the speed of sound w/o reliable air speed readings) is something that is real. He also told me that if rough weather hit during one of his rest periods he would always end it and go into the flight cabin.