The Silver Menace by Murray Leinster

Shining slime crawled up the small floats at the ends of the lower wing. It crept along the under surface, and then dripped in thick ropes down to the surface below. When contact was established the ropes grew fat and wider, until they were like shining columns from the silver sea to the now heavily weighted plane. The disgusting stuff crept over the edges of the lower plane, and began to spread over its upper surface. Other masses began to creep up the struts that separated the lower plane from the top.

The three men began to work like mad. They tore strips from the roof of the cabin and began feverishly to scrape off and thrust away the insistently advancing enemy. The plane was a large one, however, and no sooner had they scraped clear one portion of the plane than another portion was covered even more thickly than the first. The cabin itself began to be attacked. Its lower portion already glistened like metal, and in a little while the silvery film began to cover the glass of the windows. Nita began to be frightened. Parts of the roof had been torn away to provide the three men -- Davis, Gerrod, and the engineer -- with the means of fighting the creeping horror. When the slime reached the roof and began, to pour down the opening there, the whole cabin would become a terrible, suffocating tank of the horrible stuff. Evelyn spoke quietly, though with a white face.