Can one travel by air on Rosh Chodesh??
Yes one may travel by air on Rosh Chodesh. There is no prohibition against doing melacha on Rosh Chodesh, only on Shabbos and Yom Tov. Although there are certain melachos that women have a custom not to do on Rosh Chodesh, such as laundering clothing or sewing, there is no minhag not to travel by car or by plain.