Choir practice in an enclosed space (probably with standard airconditioning and/or little ventilation), with the median age being 69 and no social distancing measures.

vs.

Being in a plane with social distancing rules (unless I'm missing something), younger people and (I'm assuming) no singing and very little talking. Modern planes supposedly have pretty good air filtration systems as well.

I'm not saying there's no risk, and I definitely agree that the housemate is being unnecessarily careless in taking this non-essential trip, but presenting pretty much the worst case scenario when it's not even Lightroom herself taking the trip seems overblown.