[FG28_Kodiak]

No it's not possible directly but you can create a "in memory" mis - file. And load it to the main mission.

for example

internal ISectionFile CreateNewPlaneAtAirfield()
        {
            ISectionFile f = GamePlay.gpCreateSectionFile();

            f.add("AirGroups", "BoB_LW_StG2_II.03", "");
            f.add("BoB_LW_StG2_II.03", "Flight0", "1 2 3 4 5 6");
            f.add("BoB_LW_StG2_II.03", "Class", "Aircraft.Ju-87B-2");
            f.add("BoB_LW_StG2_II.03", "Formation", "VIC");
            f.add("BoB_LW_StG2_II.03", "CallSign", "30");
            f.add("BoB_LW_StG2_II.03", "Fuel", "100");
            f.add("BoB_LW_StG2_II.03", "Weapons", "1");
            f.add("BoB_LW_StG2_II.03", "SetOnPark", "1");
            f.add("BoB_LW_StG2_II.03", "Idle", "1");
            f.add("BoB_LW_StG2_II.03", "Skill", "0.3 0.3 0.3 0.3 0.3 0.3 0.3 0.3");
            f.add("BoB_LW_StG2_II.03_Way", "TAKEOFF", "298417.47 127327.45 0 0");

            return f;
        }

Then you can load it with

GamePlay.gpPostMissionLoad(CreateNewPlaneAtAirfield());

For more example take a look on
Tanks from narvy (added as atachment)