Voice box cancer

hi,it’s my first time posting, my grandad as just been diagnosed with cancer of the voicebox stage 2 is all I know. He’s had surgery witch was the laser treatment and then will find out on the 27th whether he needs radiotherapy or not. He’s flying on the 28th which we as a family are not happy about, so can I have advice on whether he should be flying so soon after his op and before he even knows about what’s the next step? He’s not well his cough is awful getting worse, and his weight is shocking. I jut don’t think it’s wise to fly just yet.