Insh'allah is Arabic, approximately "God Willing". It is an extremely common expression. For at least some Muslims, it is required whenever you speak of the future. I'll meet you at the restaurant at 5, insh'allah. To leave it out would be to disrespect Allah, since if he does not will it, you won't arrive.
The Hajj, the pilgrimage to Mecca, is utterly huge. Something like two million people fly in every year, all at roughly the same time. Expats living in Saudi, especially Jeddah where all the pilgrim flights land, get wonderful deals on flights out since the airlines don't want to bring the machines home empty.
So there's a planeload of foreigners coming in to Karachi and the Captain comes on "We have begun our descent into Karachi airport and will be at the terminal in ten minutes, inshallah."
On a related note, Persian fardad, Arabic bokhra and Spanish manana all carry roughly the same meaning, literally tomorrow but in practice a vague and general word used in stalling, procrastinating, etc. I think the other two learned that usage from the Arabs.
Malesh is another handy Arabc word, with a meaning somewhere between "no problem"/"no worries" and "who cares"/"screw it".
There are T-shirts with the IBM logo linked to the words Inshallah, Bokhra, Malesh".