Any person, state board, organization, or body politic may make complaint in writing to the Commission that any rate, fare, charge, classification, rule, regulation, or practice of any common carrier or restricted common carrier by aircraft, in effect or proposed to be put into effect, is or will be in violation of §§ 5.1-121 to 5.1-124, or § 5.1-133. Whenever after hearing, upon complaint or in an investigation on its own initiative, the Commission shall be of the opinion that any individual or joint rate, fare, or charge, demanded, charged, or collected by any common carrier or restricted common carrier by aircraft or by any common or restricted common carrier by aircraft in conjunction with any common carrier by railroad, motor vehicle, express and/or water, or any classification, rule, regulation or practice whatsoever of such carrier affecting such rate, fare, or charge or the value of the service thereunder, is or will be unjust or unreasonable or unjustly discriminatory or unduly preferential or unduly prejudicial, it shall determine and prescribe the lawful rate, fare, or charge or the maximum or minimum rate, fare, or charge thereafter to be observed, or the lawful classification, rule, regulation, or practice thereafter to be made effective.