Try not to focus too much on what the scales say. Remember how well you stuck to plan whilst away and how good it felt to be eating healthy, wholesome food.
Be proud of the fact that you were in control - you didn't let things slip just because you were away. That is one hell of an achievement, and something I know a lot of us would struggle with doing.
As mentioned, flying can also cause water retention, so that could be an explanation? Stick to plan again this week and I'm sure you'll see a fantastic result next week! Sometimes it can take our bodies a week or so to catch up.
Well done for having such great willpower and staying in control of things.