Complex sentence: Safety matches are classified as dangerous goods, "U.N.1944, Matches, safety," and they are not universally forbidden on aircraft; however, they must be declared as dangerous goods and individual airlines and/or countries may impose tighter restrictions.
Split into simpler sentences: Safety matches are classified as dangerous goods, "U.N.1944, Matches, safety". They are not universally forbidden on aircraft; however, they must be declared as dangerous goods and individual airlines and/or countries may impose tighter restrictions.