My friend took her LO to Spain not long after she was born, and they were ok, and her LO took it well.
As for planes in early pregnancy , i think if you havent had any problems so far, you should be ok. the only time I was told not to go on a plane was when they diagnosed me with a blighted ovum last year and were worried that I may miscarry back at the worng time - on a plane.
Nevertheless i didn't listen, and scared as I was throughout the whole holiday, i was fine.
being on a plane in early pregnancy is more to do with if you get into a sticky situation, you wont have the help you need.