At the memorial service the principal says that it's been 39 days since 39 loved ones had died. But there were 40 students on the plane and 4 chaperones, making the total 44. Now 7 people got off the plane which means 37 people related to that memorial service actually died, not 39. Two pilots would make up the numbers, but there would be flight crew too, which still leaves the numbers off.
The filmmakers originally had an ending in which Alex grabs the cable that lies on Clear's car, Alex catches fire and dies. Then Clear gets her baby and Carter survives. The test audience didn't like this, so the filmmakers shot another ending in which Alex is decapitated by a crashing police helicopter. But again, the test audience didn't like the fact that Alex dies, so they shot the finish with the billboard, which took 6 days to film and cost nearly $2,000,000.