Hi, I'd like to know the general guidelines or tips when flying with a drone. Spark will be in my cary-on bag.
I have the Spark with 3 batteries - 1 on Spark, 2 extras in a lipo bag.

1. Am I allowed to bring a total of 3 batteries on the plane?
2. Do ALL the batteries need to be less than 50% charged?

I took my Spark and batteries on several flights, no issues.. always fully loaded

Batteries shoul be 30% charge or less and the connectors should be covered.  No limit on number of Spark batteries.  Bought these at Amazon and they work great. http://a.co/ckzoTdV

Flew with my Spark and 4 batteries at 100% last month. No problems.

I always put the batteries in zip lock baggies separately, never had any issues with TSA

For what it's worth, the last time my P4 backpack went through the X-ray machine (a week ago), the 2 guys watching the screen suddenly started chuckling and the one guy said something like "Just let it go, man".  I dunno if it was because all the equipment and wires looked suspicious on the screen or what.  Or maybe it was because I had a few adult items in my P4 backpack as well.

I just flew across country and in my carry on we're 6 P4P batteries, 4 Mavic batteries and 4 Spark batteries with no problems.

Wow guys thanks a lot for the input! I guess 3 spark batteries will do fine!