function refreshGeneralInfo(){
  var utc_time = document.getElementById('utc-time');
  var local_time= document.getElementById('local-time');
  var num_aircrafts_receivable = document.getElementById('num-aircrafts-receivable');
  var num_aircrafts_valid = document.getElementById('num-aircrafts-valid');
  var num_aircrafts_located = document.getElementById('num-aircrafts-located');
  var num_aircrafts_inView = document.getElementById('num-aircrafts-inView');


  utc_time.innerHTML = getTimeString(false);
  local_time.innerHTML = getTimeString(true);
  num_aircrafts_receivable.innerHTML = AircraftsVisible.receivable;
  num_aircrafts_valid.innerHTML = AircraftsVisible.valid;
  num_aircrafts_located.innerHTML = AircraftsVisible.located;
  num_aircrafts_inView.innerHTML = AircraftsVisible.inView;

  // OGN (O) and FLAwA (F) are external sources for which no ac count exists!
  ["A", "M", "L"].forEach(function(srcId){
    // values from AircraftsVisible are already prepared (null!=0)
    replaceHtml(document.getElementById('acCountBySource-'+srcId), AircraftsVisible.countBySource[srcId]);
  });
}

// replace html in element if it has changed, else leave unchanged (reduce dom events)
function replaceHtml(element, html){
    if(element.innerHTML == html) return; // no change
    else element.innerHTML = html;
}

function refreshSelectedPlaneInfo(){
  selected_plane_infos = document.getElementById('selected-plane-infos');
  var p = planes.get(highlightedPlane);
  if(p === undefined){
    selected_plane_infos.style.display = 'none';
    return false; //cannot display details to non-existing plane
  }

  // all dom elements for plane details in sidebar
  var reg_id = document.getElementById('reg-id');
  var mode_s = document.getElementById('mode-s');
  var ac_type = document.getElementById('ac-type');
  var ac_category = document.getElementById('ac-category');
  var flight_id = document.getElementById('flight-id');
  var orig_airport = document.getElementById('orig-airport');
  var orig_airport_label = document.getElementById('orig-airport-label');
  var orig_airport_flag = document.getElementById('orig-airport-flag');
  var dest_airport = document.getElementById('dest-airport');
  var dest_airport_label = document.getElementById('dest-airport-label');
  var dest_airport_flag = document.getElementById('dest-airport-flag');
  var heading = document.getElementById('heading');
  var speed = document.getElementById('speed');
  var altitude = document.getElementById('altitude');
  var v_rate = document.getElementById('v-rate');
  var ac_lat = document.getElementById('ac-lat');
  var ac_lon = document.getElementById('ac-lon');
  var distance = document.getElementById('distance');
  var datasource = document.getElementById('datasource');
  var last_signal = document.getElementById('last-signal');
  var squawk = document.getElementById('squawk');

  // fill dom elements with infos
  if(p.reg && p.reg != "") {
    if(!p.reg.includes("state")){ // create link if reg doesn't include 'state'
      replaceHtml(reg_id, '<a href="https://planespotters.net/search?q='
          + encodeURIComponent(p.reg) + '" target="_blank">' + p.reg + '</a>&nbsp;');
    } else { // just display reg without link else
      replaceHtml(reg_id, p.reg + '&nbsp;');
    }
  } else { // if there is no reg info at all
    replaceHtml(reg_id, 'n/a');
  }

  replaceHtml(mode_s, replaceUnavailable(p.hex) + '&nbsp;');
  replaceHtml(ac_type, replaceUnavailable(p.typ) + '&nbsp;');
  replaceHtml(ac_category, replaceUnavailable(p.cat) + '&nbsp;');
  replaceHtml(flight_id, replaceUnavailable(p.fli) + '&nbsp;');
  replaceHtml(squawk, replaceUnavailable(p.squ) + '&nbsp;');


  /* Flight Details Row 1 */
  replaceHtml(orig_airport, replaceUnavailable(p.org) + '&nbsp;');
  replaceHtml(dest_airport, replaceUnavailable(p.dst) + '&nbsp;');

  var origAirportInfo = resolveAirportById(p.org);
  origAirportInfo.applyFlag(orig_airport_flag);
  replaceHtml(orig_airport_label, replaceUnavailable(origAirportInfo.label));

  var destAirportInfo = resolveAirportById(p.dst);
  destAirportInfo.applyFlag(dest_airport_flag);
  replaceHtml(dest_airport_label, replaceUnavailable(destAirportInfo.label));

  /* Flight Details Row 2 */
  replaceHtml(heading, replaceUnavailable(p.trk) + '&deg;');
  replaceHtml(speed, replaceUnavailable(p.spd) + '&nbsp;kt');

  /* Flight Details Row 3 */
  replaceHtml(altitude, replaceUnavailable(p.alt) + "&nbsp;ft");
  if(p.vrt) {
      replaceHtml(v_rate, replaceUnavailable(p.vrt) + ' ft/min</td>');
  } else {
      replaceHtml(v_rate, "");
  }

  /* AC Tracking Row 1 */
  replaceHtml(ac_lat, replaceUnavailable(p.lat) + '&deg;');
  replaceHtml(ac_lon, replaceUnavailable(p.lon) + '&deg;');

  /* AC Tracking Row 2 */
  if(!historyModeEnabled){
    replaceHtml(distance, replaceUnavailable(p.dis).toFixed(1) +'&nbsp;'+ mapInfo.distunit);
  }

  if(p.src == 'A') {
    replaceHtml(datasource, 'ADS-B');
  }
  else if (p.src == 'M') {
    replaceHtml(datasource, 'MLAT');
  }
  else if (p.src == 'F') {
    replaceHtml(datasource, 'FlightAware');
  }
  else if (p.src == 'O') {
    replaceHtml(datasource, 'OGN Flarm');
  }
  else if (p.src == 'L') {
    replaceHtml(datasource, 'Local Flarm');
  }
  else {
    replaceHtml(datasource, '&nbsp;');
  }

  /* AC Tracking Row 3 */
  replaceHtml(last_signal, replaceUnavailable(p.lla) + '&nbsp;sec');

  selected_plane_infos.style.display = ''; // reveal/un-hide table

  return true;
}