In this video, Stewart uses a lot of dramatic irony by using clips of newscasters stating their preposterous ideas of what could have happened to the plane, even though Stewart and the audience both know that these things such as the plane getting sucked into a black hole could not have possible happened. Although this video shows a lot of dramatic irony, Stewart also uses a lot of verbal irony to get his point across. In most cases, he uses verbal irony in the form of sarcasm.
Stewart is not intending to make fun of the newscasters, but instead he is trying to make fun of Republicans in general. Not as much in the video above, but especially during presidential elections, Stewart is seen using his satirical techniques to make fun of the Republican candidates. The overall agenda of the show is to poke fun at people, usually Republicans, using his satirical techniques.