If you have been called for an interview at short notice, firstly congratulations, secondly explain you don't have a power point to hand but can happily draw out the theory on paper or whiteboard. They will understand and will enjoy the dynamic nature of the presentation. Use your ATPL notes as a starter.
As everyone else has said, explaining someone else's presentation is always a bit hollow , especially when they get you to explain what all the TLAs mean. They will see through you.
Good luck.