If I had an airline ....

All boarding signs would be computer monitors and there would be two lanes, both showing a red cross until boarding commenced. They'd go:

X, X
Group 1, X
Group 1, Group 2
Groups 1&2, Group 3
Groups 1-3, Group 4
Groups 1-4, Group 5
Closed, Closed

And I'd hand out kettle crisps to people as they boarded, before asking for a government bailout then going bankrupt. But it'd be fun.