Four Boeing employees called in tips to a Federal Aviation Administration whistleblower hotline to report issues with technology on the 737 MAX-8 plane one day after the Ethiopian Airlines crash, CNN reports. The 737 MAX-8 has been involved in two crashes that killed 346 people in total, and have since been grounded worldwide. The former and current Boeing employees reportedly described issues related to the angle of attack sensor—a vane that measures the plane's angle in the air, and the anti-stall system called MCAS. One tip concerned a previously unreported issue of damage to the wiring of the angle of attack sensor due to a foreign object. The FAA told CNN it has reviewed the tips, and may be opening up an entirely new investigative angle. Directly after the Ethiopian Airlines crash investigators found that a malfunctioning angle of attack sensor was sending incorrect data to the MCAS system. Boeing's CEO will hold a news conference Monday following a shareholder meeting in Chicago. International civil aviation authorities are also meeting on Monday to discuss issues surrounding the 737 Max.