a packaging machine for thermoforming plastic packages , filling them with the desired contents , and sealing them under vacuum or gas if desired , wherein a train of packages move through the machine in a horizontal path at substantially constant speed , the machine including reciprocating interacting package forming and sealing elements with support means acting simultaneously on the upper and lower sides of the train of packages as they move through the machine . in an alternate arrangement , lids may be applied to package portions preformed by separate apparatus .