Does anyone know if it's safe to fly✈ 4 hours to another state in your second Trimester?

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Hi I'm about 20 weeks and I'm in California and I'm about to fly to Texas in 2 days.. Just curious if anyone knows if it's safe to fly in your second trimester or during pregnancy at all. Im not having any pregnancy complications but, I did have 2 miscarriages before this healthy pregnancy which only lasted to about 7 or 8 weeks. I'm 20 weeks now. I tried getting a hold of my OBGYN but, shes busy and the office is closed.. Does anybody know or have experience traveling by plane and delivering a healthy baby????...