Price discrimination by the Airlines is legal because,Airlines
can establish competition among other Airlines by setting low
prices which attracts more people who are sensitive to prices.
Price discrimination increases Revenues for Airlines.
It is also legal because it involves different prices,
different sets of consumers for the same good.
It is not means of discrimination because if some people have
inelastic demand that is if they are willing to pay higher
price,then there is no fault in Airlines setting higher prices for
increasing Revenue and profits.
Here the price discrimination is not done on the Race,
Religion, Nationality or gender.hence it is legal.
It is not causing a violation of Anti Trust or price fixing
laws.