Mildly elevated LFT's in the absence of a known major cause of liver disease are unlikely to fail you a Class 1 medical, but it might need to be monitored, and ultimately finding a cause is a good thing.
A few thoughts.
1. treat excess alcohol with disdain ! Also have a look at how much coffee you drink.
2. Keep you BMI well under 25 if you can - fatty liver is the most common modern cause of liver injury
3. See a skilled physician with knowledge of liver disease - there is a list including many of the things noted above, that need to be thought about and excluded.If its your transaminases elevated you won't have a bile duct cause.
4 if you have been born or raised in a Hepatitis prone area like Asia or India, you may have caught hep B or Hep A years ago and its catching up with you. Another scenario would be Hep b or C post past blood or sexual contact, and not picked up.
5 occasionally liver disease can be due to autoimmune processes or exogenous substances , and this is quite specialised .Dont take anything that isn't normal food! If you have joint pains or rashes of other medical symtpoms that may offer a clue to the physician.