May be he already contain the pressure too much too long, just you didn't notice. Women talk to release pressure, men don't and prefer keep silence.
This is the the straw that broke the camel's back - hopefully you can figure what happened before he raised the issue to travel with friend. Many men have to illusion that women are understanding and should knew what he think or feel because she like details.
Did you notice small thing he did and praise him? Did you notice any change?