For over a year, ABC News correspondent Bob Woodruff and team have been traveling the world to investigate the deadly Boeing 737 MAX-8 airplane, grounded last year following two tragic crashes that killed 346 passengers from around the world. On the heels of the 737 MAX’s recent clearance to fly again next month, “20/20” reports this Friday night on the aircraft’s controversial flight control software and how it mistakenly sent planes into deadly nosedives. “20/20” also investigates what Boeing knew about concerns with that flight control system and when they knew it.