We were doing so well

Ainsley has been a very good sleeper. About 3 weeks ago, she started sleeping through the night at 6 weeks old. She did it for about a week. Then we went on vacation. She was completely thrown off due to the travel. She didn't sleep during the plane trips. We got there and she was back to getting up once a night. Now we are home and I was hoping she would slip right back into her schedule. Apparently I was wrong. For the first few nights since we have been back, she has continued with the up once a night thing. Not last night though. She was up twice last night. She hasn't done that since she was 2 weeks old. What's happening? I have less than 3 weeks until I go back to work and I was really hoping she would be sleeping through the night by then. I guess alot can still change in 3 weeks.