Low lying placenta and travel

Hi this is a very specific questions, hoping someone could shed some light as my midwife is away for 2 weeks. I’m due to travel abroad at 28 weeks pregnant and need a fit to fly letter (I’ve been through all this with my midwife and I’m healthy etc and we’ve agreed it will be fine) however since my 20 week scan I’ve found out I have a low lying placenta and I keep reading that they don’t issue the fit to fly letter if you have this. Has anyone had any experience with this? Thanks