Undoing the changes in 97939 brings back the TU reservation system. Additionally, reaction fire was not broken before, but it might as well have been because there were no TUs being reserved (and I am not nearly clever enough to survive without that feature).
I have attached a very simple patch that rolls back the changes in 97939. This patch should be applied against 27965. More recent revisions may or may not apply cleanly.
To use this patch:
* Place the tu_fix.diff into your ufoai source code directory (the same place you run ./configure, make, etc)
* Open a terminal, go to that directory, and run the following
patch -p0 < ./tu_fix.diff
Edit: Forgot to attach the file!