The F/O probably forgot to call the Capt "Sir"
Last time I jump seated on AI, I was stunned to hear the F/O address the Capt by Sir this......... and Sir that..........
Hostee comes in and says do you want coffee sir
Laughing out aloud was hard to control. Especially when picturing myself addressing my Capt's as Sir. I'd probably get a slap for calling them Sir.
In which other airlines do you have to address the Capt as Sir?