Hi mama! Okay so I haven't personally brought a fetal doppler on a plane, but honestly I'd call Cebu Pacific customer service directly this morning para sure, they're usually helpful with questions about medical devices, and doppler falls under that category kaya better safe than sorry! A few of us moms have brought other pregnancy stuff like maternity pillows and compression socks without issue, but doppler is a bit different so best to confirm with them first before you head to the airport. Safe travels!