One of the world's most reliable barometers of the state of the aviation and space industries swings into action tomorrow as the romance and business of flight come together for the 50th Paris Air Show.
For tens of thousands of visitors, the show does not actually start until the exhibition opens to the public from Friday.
It is in the four days preceding general admission, when the show is restricted to aerospace professionals and the media, that eyes will be focused on the commercial aspects of air travel for civilian, business and defence purposes.
Announcements of major orders and significant trade developments are essential features of the show, offering a useful guide to whether the medium-term prospects for aviation suggest a smooth flight or a period of turbulence.
Global preoccupation with cost-cutting means there will be notable absentees from the event.
Aviation Week magazine has reported that in view of the likely non-attendance of some defence contractors from the United States, "2013 may hit a low mark not seen for many years".
There is expected to be no sign of the world's fourth-largest defence manufacturer, Northrop Grumman, along with certain other key figures from military aviation at the show.
The magazine says the reduced defence turnout, in terms of flying display, will be "accentuated this year by the US defence department's decision not to send any hardware" amid sharp budget cuts.
On Wednesday, Bloomberg reported the Pentagon sent congress details of US$37 billion in sequestration cuts affecting defence contractors from Lockheed Martin to Huntington Ingalls Industries.
The American air force's US$2.5 billion deal to buy 19 F-35 jets made by Lockheed reflects a sequestration cut of $503 million, according to the report. The Navy's final $808m to buy four carrier-model F-35s incorporates a $157m cut, and its $1bn for six Marine Corps short take-off and vertical landing fighters reflects a $146m reduction.
Defence companies will be able to use the report to determine "what funding is available for that particular programme for the fiscal year," says John Roth, the Pentagon's deputy comptroller for programmes.
The air force's final $82m on 717 laser-guided Lockheed Hellfire missiles fired by Predator and Reaper drones incorporates a cut of $313,000.
All the same, the aviation extravaganza in Paris holds undiminished appeal for aerospace professionals and aviation enthusiasts alike.
The last Paris show, held in 2011, was said to have attracted record attendance figures: 151,500 professional visitors, according to officials; 204,000 members of the public; and 3,250 journalists from 80 countries. The numbers are likely to be similar or better this year.
At the 2011 event, two giants of the industry - Airbus and Boeing - both announced significant new business.
Airbus, the French aircraft manufacturing division of the European aerospace group EADS, provoked excited media comment in France after carriers placed orders worth $88bn for more than 900 new planes. The European contractor accordingly "defeated its great rival Boeing" in the words of a French trade magazine, L'Usine Nouvelle, a judgement shared by the anglophone trade press.
The US manufacturer nevertheless announced orders for 141 aircraft with a total value of $22bn. And Boeing's delegation headed for this year's Paris show buoyed by a huge order by Singapore Airlines, described as one of biggest in the carrier's history, for 30 780-10 aircraft, the planned new stretch version of the Dreamliner.
If delivered, this would make the airline Boeing's launch customer for the plane and present business worth $17bn to the manufacturer and its main production partners.
Singapore Airlines says the order is conditional, subject to Boeing quickly ending uncertainty on whether the project will go ahead. Boeing has yet to announce formally that production of the 787-10 is to begin but a statement seems on the cards and some industry observers are speculating it could come at the Paris show.
Air Transport World, a website based in the US, recalls that Boeing's chief executive, Jim McNerney, said in April that the company expected to launch the 787-10 programme "sooner rather than later".
Boeing was coming under pressure from airlines to announce the go-ahead, Mr McNerney said then, adding: "The one thing we don't lack for with the 787-10 is demand. Customers are pushing for us to get this airplane out." The Singapore order would represent an important boost for Boeing after a difficult start to the year when its global 787 fleet was grounded because of concerns about overheating lithium-ion batteries.
Air Transport World also raised the possibility that the Paris event would be chosen for the launch of the Brazilian maker Embraer's second-generation E-Jet.
Airbus will again be busy during the show. Visitors will see static and in-flight displays of the turboprop A400M Atlas military transporter, which caused some embarrassment when failing to get airborne at the 2011 Paris air show.
Teething troubles overcome, Airbus expects soon to start deliveries of the aircraft to customers, starting with the French and Turkish air forces.
The company will also display its A380-800, the world's largest passenger aircraft, a wide-bodied, double-decked plane that carries 525 people and first entered service in 2008 with a flight from Singapore to Sydney.
The Paris show, established in 1909, is held every two years, alternating with its equivalent event in Farnborough in the United Kingdom.
The French show takes place at Le Bourget, an airport 11 kilometres north of the French capital that has not been used for passenger flights for nearly a quarter of a century.
Now, the airport is restricted to business use and exhibitions although it is also the headquarters of the French air accident investigation bureau.
The world was still in the grip of the Cold War between Moscow and its Warsaw Pact allies and the West when a Soviet Tupolev Tu-144 plane crashed during the 1973 Paris Air Show. The accident claimed the lives of 14 people, all six on board and eight on the ground as 15 houses were flattened.
Theories about the cause included suggestions the crew exceeded the aircraft's capabilities in an attempt to outperform the Concorde and that it crashed while trying to dodge a French Mirage military jet trying to photograph the plane. Evidence of Russia's continuing military strength will be seen at this year's show, with plans for daily demonstration flights of the twin-engined Sukhoi Su 35 fighter jet built by the country's largest aircraft manufacturer, the Komsomolsk-on-Amur Aircraft Production Association.
The week-long air show is described by its organisers, the French aerospace industry's main representative body, Gifas (Groupement des industries françaises aéronautiques et spatiales), as the world's oldest and largest of its kind. Gifas says the show is a major networking occasion, its history placing it "at the very heart of the development of the world aviation and space industry".
Emeric d'Arcimoles, the chairman of Salon du Bourget, the Gifas subsidiary that runs the show, spoke of enormous interest in the event when he held a press conference in London in April.
Listing improvements on previous shows, he said 54,000 square metres of exhibit stand space would be occupied and pointed out, as if to minimise the effect of absences, the US pavilion would be 10 per cent larger than at the 2011 show. The host country will dominate with its own "village" serving as a showcase for 400 companies.
And despite the scaled-down presence or non-appearance of some military and business contractors, the organisers point out Dassault, Gulfstream, Bombardier and Embraer will all be involved. Indeed, on Wednesday, the French defence minister, Jean-Yves Le Drian, was quoted by the financial daily Les Echos as saying France expected to make its first deliveries of Dassualt Aviation's Rafale warplanes to India by 2016 or 2017.
The paper said France's draft defence budget was based on an assumption that the first deliveries of the fighters would start in 2016.
India picked the Rafale for exclusive negotiations in January 2012 after a hotly contested bidding war with rival manufacturers, but is still to finalise the $1bn deal. Much interest in Paris is also expected to focus on Comac, the state-owned Chinese manufacturer created in 2008 with the aim of weaning the country off its dependency on the big western suppliers.
More than 20 aircraft are expected to take part in the daily flying displays. The crews will hope for an ease of movement that is unlikely to be replicated at ground level.
On the floor, visitors and exhibitors will receive alerts from a temporary radio station to help them cope with the formidable congestion that brings roads around Le Bourget to a standstill during each show.