This script is designed to be used as a script that runs after a save event. It's based on default 'Save Extra JPEG' and will save a PNG next to the current active if 'X-Plane' or 'Aircraft' are presented on path. This script does not handle 'as a copy' when saving.

SavePNG4XP.jsx

/**
 * Developed by Mário Valney <mariovalney@gmail.com>
 *
 * Inspired on "Save Extra JPEG" and created using:
 * https://www.adobe.com/content/dam/acom/en/devnet/photoshop/pdfs/photoshop_scriptref_js.pdf
 */

/**
* @@@BUILDINFO@@@ Save PNG 4 XP.jsx 1.0.0 Thu Oct 24 2019 19:21:44 GMT-0300
*/

var begDesc = "This script is designed to be used as a script that runs after a save event. It's based on default 'Save Extra JPEG' and will save a PNG next to the current active if 'X-Plane' or 'Aircraft' are presented on path. This script does not handle 'as a copy' when saving."
var begName = "Save PNG 4 XP"

try {  
    if ( ! IsSaveEvent( arguments[0] ) ) {
        alert( 'Save PNG 4 XP should only be used with the Save Document event. Aborting...' );
        throw( "DONE" );
    }

    var data = GetDataFromDocument( activeDocument );

    /**
     * Check it's inside XP environment and if the current file
     * is not already a PNG one. Then save PNG.
     */
    if ( ! data.fromXP || 'png' == data.extension.toLowerCase() || 'PNG' == data.fileType ) {
        return;
    }
    
    if ( UsingAsACopy( arguments[0] ) ) {
        alert( 'Saving "As A Copy" may not save the X-Plane PNG correctly.' );
    }
    
    SavePNG4XP( data );
} catch( e ) {
    // Remove comments below to see error for debugging 
    // alert( e );
}

/**
 * Will save the current document as a copy using PNG.
 * - Compression: none
 * - Interlaced: none
 * 
 * @param {object} Return of GetDataFromDocument function
 */
function SavePNG4XP( data ) {
    var options = new PNGSaveOptions();
    options.compression = 0;
    options.interlaced = false;
    
    // Check we are using extension today
    var extension = ( "" == data.extension ) ? '' : '.png';

    // Third option is as a copy, set that to true 
    // so the activeDocument doesn't switch underneath the user
    activeDocument.saveAs(
        File( data.folder + '/' + data.fileName + extension ),
        options,
        true
    );
}

/**
 * Find the options "as a copy" is active.
 * 
 * @param {ActionDescriptor}
 * @return boolean
 */
function UsingAsACopy( actionDescriptor ) {
    if ( undefined == actionDescriptor || "ActionDescriptor" != actionDescriptor.typename ) {
        return false;
    }

    var keyCopy = charIDToTypeID( "Cpy " );
    if ( ! actionDescriptor.hasKey( keyCopy ) ) {
        return false;
    }

    return actionDescriptor.getBoolean( keyCopy );
}

/**
 * Check the description is about "saveStage" but not "saveBegin".
 * 
 * @param {ActionDescriptor}
 * @return boolean
 */
function IsSaveEvent( actionDescriptor ) {
    if ( undefined == actionDescriptor || "ActionDescriptor" != actionDescriptor.typename ) {
        return false;
    }

    var keySaveStage = stringIDToTypeID( "saveStage" );
    if ( ! actionDescriptor.hasKey( keySaveStage ) ) {
        return false;
    }

    var typeSaveStage = actionDescriptor.getEnumerationType( keySaveStage );
    var typeSaveStageType = stringIDToTypeID( "saveStageType" );
    var enumSaveStage = actionDescriptor.getEnumerationValue( keySaveStage );
    var enumSaveStageBegin = stringIDToTypeID( "saveBegin" );
    return enumSaveStage != enumSaveStageBegin || typeSaveStage != typeSaveStageType;
}

/**
 * Get data from Document to be used on script
 * 
 * @param {Document} The activeDocument
 * @return object {
 *      folder      {string}
 *      fileName    {string}
 *      fileType    {string}
 *      extension   {string}
 *      fromXP      {boolean} True if we have X-Plane or Aircraft on document path
 * }
 */
function GetDataFromDocument( inDocument ) {
    var fullPathStr = inDocument.fullName.toString();
    var lastDot = fullPathStr.lastIndexOf( "." );
    var fileNameNoPath = fullPathStr.substr( 0, lastDot );
    var lastSlash = fullPathStr.lastIndexOf( "/" );
    
    var data = new Object();
    data.folder = fileNameNoPath.substr( 0, lastSlash );
    data.fileName = fileNameNoPath.substr( lastSlash + 1, fileNameNoPath.length );
    data.fileType = inDocument.fullName.type;
    data.extension = fullPathStr.substr( lastDot + 1, fullPathStr.length );
    data.fromXP = fullPathStr.lastIndexOf( "X-Plane" ) > -1 || fullPathStr.lastIndexOf( "Aircraft" ) > -1;

    return data;
}