Hey there, thanks for playing Passing By :)
Sorry that you became stuck in such an unfortunate situation. If it isn't too dire, maybe you could try quickly dropping a few heavy items in your inventory, especially balloon designs and sandbags. That would allow your balloon ship to ascend more quickly.
If that doesn't help, you could also send me your savegame at studio-windsocke.help [at] posteo.de. The file is called journey.save and can be found in <User>/AppData/LocalLow/Passing By/Passing By/ (Windows) or <User>/Library/Application Support/Passing By/Passing By/ (Mac). Maybe I could find a way to help you so you don't have to start over. :)