Today, the trend is to increase {TAIL ~ the temperature} of operation of {HEAD ~ gas turbine engines} 
Today , the trend is to increase { TAIL ~ the temperature } of operation of { HEAD ~ gas turbine engines }
OTH OTH OTH OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD