NEW YORK ( TheStreet) -- Airline stocks have been flying high in the sky so far in 2013. Today I profile 11 airlines and nine of them report quarterly results next week. All are flying well above their 200-day simple moving averages, which reflects the risk of a reversion to the mean particularly given that three are rated hold and eight are rated sell according to ValuEngine.All 11 airline stocks are overvalued, seven by more than 20%. Ten of 11 are flying higher by double-digit percentages over the last 12 months except one, which is down by less than 5%. Nine are higher by 26.1% to 114.2%. All are projected to be at lower altitudes 12 months from now. The airline industry is 20.6% overvalued in a market that's trading under a ValuEngine valuation warning with 75.3% of all stocks overvalued, and with 42.2% of all stocks overvalued by 20% or more. We still show that 15 of 16 sectors are overvalued, 13 by double-digit percentages. Given this investment environment investors should not be adding to positions in airlines and should consider taking profits before these earnings reports are released next week. Investors should reduce allocations to stocks to 50% of their equity market allocations.