When lightning strikes, it tears apart the bond in airborne nitrogen molecules. Those free nitrogen atoms N2 nitrites then have the chance to combine with oxygen molecules to form a compound called nitrates N3. Once formed, the nitrates are carried down to the ground becoming usable by organisms. Will it react with the oxygen in the air spontaneously, the answer is no. The mixture is chemically stable indefinitely. A mixture with air near the release point can be ignited, but if this does not happen then when its concentration gets below 4% it will be unable to carry a flame.
A nitrite (NO2) is a nitrogen atom bonded to only two nitrogen atoms. Very strong bond.
A nitrate (NO3) is a nitrogen atom bonded to three oxygen atoms. Weaker bond