A parliamentary panel has asked the civil aviation ministry to cap the upper and lower levels of airfares, and ensure that predatory pricing mechanism is not adopted by the airlines under the cloak of free market economy. "A perfect balance has to be maintained between the commercial interest of the private airlines and the interest of the passengers so as to enable the private airlines to grow and at the same time the interest of passengers should also be kept in mind, so that they are not fleeced in the garb of commercialisation," the panel said.