I would has at an educated guess that the reference to fitting of Hushkit to Travolta's acft. in 89 was a Comtran Stage 2 Hushkit...I stand to be corrected but as far as I am aware there was no legal requirement for Stage 3 at that time (started 95 ongoing to 2002 in EU for example, similar in US I believe) and that neither the Burbank/Quiet Nacelle S3 kits for the 707 were even in existance at that time except on the drawing board possibly (and again as far as I am aware the Burbank S3 kit does not have 'Blow In Doors' it utilises a long duct and acoustic lip/nozzles, blow in doors is the Comtran Stage 2 kit)
Whether or not a S3 hushkit makes any difference to joe public is not the issue - what is from an operators/manufacturers point of view is that legally the noise footprint is within the S3 limits for compliance
The MD80 with its' JT8D-217/219 engines is already naturally Stage 3 from design/build, the hushkit developed by Jet Engineering is actually a Stage 4 hushkit...a wonderful aircraft long may it continue
747 Focal - the Air Memphis 707 (you say without hushkit) in the picture you show is clearly fitted with the Burbank Stage 3 Long Duct Hushkit as also retrofitted to DC8-60 series. Hence as the photo caption states it is able to operate still at Ostend Airport, Belgium, the EU in March 2003.
The Travolta 707 nacelle is clearly a Stage 2 Comtran Hushkit only
Note the difference in nacelles...
