Yes you can take essences on a plane! Subjecting essences to radiation is definitely something to avoid. Storing them by the tv or microwave is not a good idea, but the short term exposure from an x ray scan doesn't seem to hurt them.
There are no limits on liquids in your checked baggage, but I'm more of a carry on only kinda girl. I just did two weeks in the African bush with a carry on bag that had to hold my tent and a bunch of energy bars as well as my usual personal stuff. The secret is a big purse.
You are allowed a quart sized ziplock bag to hold all your liquids, and each bottle can be no more than 3.3 oz. My flower essences are all 1 oz bottles, so they are in the clear. Liquid medications do not count towards your one quart limit, and flower essences will pass as medications.
I got another quart bag and stuck a slip of paper in it with "medications" written across it with a marker for my essences and an herbal tincture. Nobody questioned it. If they do, don't try to explain flower essences. Just say it helps you manage your anxiety, or that it's an antidepressant, or whatever the case may be.
This allowed me to pack sunscreen and bug spray in my allowable other quart bag.
Our number one most used essence amongst me and my two companions was Crisis Care. This essence is very multi-purpose for any "uh oh" situation. The second was a single bottle of chamomile for stress manifesting as stomach issues. We ate strange food, had diarrhea the whole time and needed the stress relief. We used Peaceful Sleep some also. With everything being unfamiliar and not entirely comfortable, and the brain buzz from the activity of the day, it was a help.
The thing we didn't use at all was the Stay Calm. It seemed like a good idea in the face of public speaking and being schlepped around by people who act like they'd learned to drive in a demolition derby. Fear never entered in at any point though and Stay Calm went unopened.
What I wish I would have packed but didn't was Yarrow Shield. Yarrow Shield is protective in spiritually dark atmospheres and boy, were we there! I'm not as sensitive to that as some, and just didn't think to pack it.
The other thing I would recommend for serious trips is some olive leaf extract. It's antiviral, antibiotic, antifungual and anti-inflammatory. If you're going to take one thing to deal with airplane germs, stressed out immune systems and who knows what, this is my pick.
I'm home, but the fun's not over yet. I get to do a parasite cleanse! So exciting...
If you've got a trip coming up, may it be safe but exciting, the food be adventurous but healthy, may your sleep be deep and restorative so you can take on the days with full energy and zeal to get as much as you can out of your time there.